Radiation therapy (radiotherapy). What is it and what is its essence? Indications, types and techniques of radiation therapy. Radiation therapy methods Stereotactic radiation therapy

Radiation therapy is a method of treating tumor diseases using ionizing radiation.

Such radiation is created using special devices that use a radioactive source. The essence of the method is that during irradiation, many mutations accumulate in actively dividing cells, which lead to their death. Tumor cells multiply much faster than healthy cells, so they are more sensitive to the effects of radiation.

There are several options for radiation therapy ( radiotherapy). First of all, they are divided by type of radiation - X-ray and gamma therapy. Depending on the location of the source relative to the human body, there is remote irradiation (at a distance), contact, and intracavitary. Radiation can be delivered directly to the tumor using thin needles (intissue irradiation). Radiation therapy This is an independent medical specialty practiced by radiation therapists. If this method of treatment is necessary, the oncologist refers the patient for a consultation with a radiation therapist, who determines the type of therapy, the amount of radiation exposure and the duration of the course.

How is RT performed?

The main task when carrying out radiation therapy is to have maximum effect on the tumor with minimal impact on healthy tissue. To do this, when planning therapy, the doctor must accurately determine the location of the tumor process in order to direct the beam in the right direction and to the desired depth. The area of ​​influence is called the irradiation field. During remote irradiation, a mark is applied to the skin indicating the area to be treated. The surrounding areas and other parts of the body will be protected by lead shields. The radiation session lasts several minutes, and the number of sessions is determined by the total radiation dose that was prescribed. The radiation dose depends on the size of the tumor and the type of tumor cells. During the session, the patient does not experience pain or any other sensations. Irradiation takes place in a specially equipped room. During the procedure, the patient is there alone. The doctor observes what is happening from the next office through a special glass or using video cameras.

Depending on the type of malignant tumor radiation therapy can be an independent treatment method or used in combination with a surgical method or chemotherapy. Radiation therapy is local in nature and can be used to target specific areas of the body. In many cases, it contributes to a significant reduction in tumor size or complete cure.

What are the complications of RT?

Side effects may appear only in the irradiated area or be general in nature. Before starting treatment, ask your doctor what complications you can expect and whether there are ways to avoid them.

Side effects depend on the area that is exposed. During remote irradiation, skin dryness, peeling, itching, redness, and the appearance of small blisters often occur. Emollient creams and lotions are used to prevent and treat this reaction. A common complication radiation therapy is weakness and fatigue. Correct sleep patterns, daytime rest, following a diet with enough calories, and walking in the fresh air will help you cope with this.

All problems should be reported to your doctor immediately, as most of them can be alleviated or eliminated. Remember that side effects, although unpleasant, are mostly temporary and will gradually subside with treatment.

More often during radiation therapy they occur local radiation reactions.

• During external beam radiation therapy, dry skin, peeling, itching, redness, and the appearance of small blisters often occur in the projection of the irradiation field. To prevent and treat such a reaction, ointments (on the recommendation of a radiologist), Panthenol aerosol, creams and lotions for the care of children's skin are used. After irradiation, the skin loses its resistance to mechanical influences and requires careful and gentle treatment.
• During radiation therapy for head and neck tumors, hair loss, hearing loss, and a feeling of heaviness in the head may occur.
• When irradiating tumors of the face and neck, dry mouth, sore throat, pain when swallowing, hoarseness, decreased and loss of appetite may occur. During this period, steamed, boiled, pureed or chopped food is useful. You need to eat small meals often. It is recommended to drink more liquid (jelly, fruit compotes, rosehip decoction, non-acidic cranberry juice). To reduce dryness and sore throat, use a decoction of chamomile, calendula, and mint. It is recommended to instill sea buckthorn oil into your nose at night, and take a few tablespoons of vegetable oil on an empty stomach during the day. Teeth should be brushed with a soft toothbrush.
• During irradiation of the chest organs, pain and difficulty swallowing, dry cough, shortness of breath, and muscle soreness may occur.
• When irradiating the mammary gland, you may experience muscle soreness, swelling and tenderness of the mammary gland, an inflammatory reaction of the skin in the area of ​​irradiation, sometimes a cough, and inflammatory changes in the throat. You need to take care of your skin using the method described above.
• When the abdominal organs are irradiated, loss of appetite, weight loss, nausea and vomiting, loose stools, and pain may occur. When irradiating the pelvic organs, side effects include nausea, loss of appetite, loose stools, urination problems, pain in the rectum, and in women, vaginal dryness and discharge. To eliminate these phenomena in a timely manner, it is better to eat a diet. The frequency of meals should be increased. Food should be boiled or steamed. Spicy, smoked, salty dishes are not recommended. If you have bloating, you should avoid dairy products; pureed cereals, soups, jelly, steamed dishes, and wheat bread are recommended. Sugar consumption should be limited. It is recommended to add butter to prepared dishes. It is possible to use drugs that normalize intestinal microflora.
• When undergoing radiation therapy, patients should wear loose clothing that does not restrict the area where the radiation is being given and does not rub the skin. Underwear should be made of linen or cotton fabric. To carry out hygiene procedures, you should use warm water and non-alkaline (baby) soap.

In most cases, all of the above changes are transient; with adequate and timely correction, they are reversible and do not cause cessation of the course of radiation therapy. It is necessary to carefully follow all recommendations of the radiologist during the treatment process and after its completion. Remember that it is better to prevent a complication than to treat it.

Based on materials from the magazine “Together Against Cancer”

What should be done to reduce the side effects of RT?

Each patient's body responds to radiation therapy differently. That is why the doctor takes into account the characteristics of your body and the characteristics of your disease when drawing up a radiation treatment plan. In addition, he will give advice on how you should behave at home, taking into account the specifics of your treatment, to reduce or prevent side effects.

Almost all patients receiving radiation therapy for a tumor disease must exercise some level of self-care to promote successful treatment and improve their condition. Some guiding principles for this are given below:

• Use more time to relax. You need to sleep as much as you want. Your body uses a lot of extra energy during treatment, and you may feel more tired. Sometimes general weakness may continue for another 4 to 6 weeks after the end of treatment.
• You need to eat well. One must have a balanced diet to prevent weight loss.
• Avoid wearing tight clothing that has tight collars or belts in the treatment area. It's best to wear old suits that you feel comfortable in and that you can wash or throw away if they get stained with marker paint.
• Be sure to tell your doctor about all the medications you are taking. If you have taken or are taking any medicine, even aspirin, your doctor should know this before starting treatment.
• Ask your doctor or radiation therapist any questions you have. Only he can properly advise you regarding your radiation treatment, side effects, home monitoring and other medical arrangements.

Additional skin care in the area of ​​radiation:

• Do not use any soaps, lotions, deodorants, medications, perfumes, cosmetics, powders or talc, or other substances on the radiation area without consulting your doctor.
• In the irradiation area, clothing should be made of loose, loose cotton fabric.
• Clothes should not be starched.
• Do not rub or scrape the skin in the area being treated.
• Do not use adhesive tape in the area being treated. If dressing is necessary, an adhesive tape with pores outside the radiation area or a bandage can be used.
• You should not heat or cool (heating pad, ice, etc.) the irradiation area. Even hot water can harm your skin. Only moderately warm water should be used for bathing and washing, especially in the area of ​​radiation.
• For shaving, if this area is exposed to radiation, it is better to use an electric razor, after consulting with your doctor. Do not use shaving lotions or hair removers.
• Protect your skin from sunlight. Before going outside, wear a hat and loose clothing to cover the exposed skin areas. Talk to your doctor about the use of sunscreens. Sometimes it makes sense to use them if you get sunburned easily and your skin is too delicate. It is necessary to protect the skin from excessive exposure to sunlight for at least one year after the end of radiation therapy.

What is the duration of RT?

The duration of the course of radiation therapy depends on the characteristics of the disease, the dose and the irradiation method used. The course of gamma therapy generally takes from 6 to 8 weeks (30 - 40 sessions). In most cases, radiation therapy is well tolerated by the patient and hospitalization is not required. For certain indications, radiation therapy is performed in a hospital setting.

Will radiation therapy make me radioactive?

No, a patient undergoing radiation treatment is safe for others and is not a source of radiation himself. The only exceptions are brachytherapy methods, when the radiation source is implanted directly into the tumor (for example, this technique is common in the treatment of prostate cancer). However, in this case, the radiation does not extend to a distance exceeding 1 cm. It is only recommended to avoid intimate contact with pregnant women and not to sit children on your lap. You will receive more detailed information from your attending physician.

Systemic RT uses radioactive substances that circulate throughout the body. Some substances can leave the body in saliva, sweat and urine before the radioactivity subsides, so these liquids are radioactive. Therefore, precautions are sometimes taken when contacting patients. Your doctor will tell you about these measures.

When is RT used?

RT can be used to treat almost any type of tumor, including cancer of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, spine, stomach, uterus, and soft tissue sarcomas. Radiation can also be used in the treatment of leukemia and lymphoma. The dose of radiation depends on many things, including the type of cancer and whether there are nearby organs or tissues that may be damaged by radiation.
In some cases of cancer, radiation may be given to areas where there is no evidence of a tumor (prophylactic RT). This is done to prevent the development of cancer.
RT is also used to eliminate or reduce symptoms (palliative RT), such as bone pain.

What is the difference between external RT, internal RT (brachytherapy) and systemic RT? When are they used?

The radiation may come from a machine outside the body (external radiation), the source of radiation may be located within the body (internal radiation), or it may use radioactive materials circulating throughout the body (systemic radiation). The type of radiation received depends on the type of cancer, its location, how deep the site needs to be irradiated, the patient's general health and medical history, whether the patient will be given other treatments, and other factors.
Most people receiving RT receive external chemotherapy. For some - external and internal or systemic, one after the other or simultaneously.

• External LT used to treat most types of cancer - bladder, brain, breast, cervix, larynx, lung, prostate and vagina. Also, external radiation therapy can be used to relieve pain or other problems when cancer spreads to other places in the body.
• Intraoperative RT (ILT) is a form of external RT performed intraoperatively. ILT is used to treat localized tumors that cannot be completely removed or are at risk of recurrence. After the tumor is removed, a large dose of radiation is delivered to the tumor site during surgery (adjacent healthy tissue is protected by a special shield). ILT is used in the treatment of cancer of the thyroid gland, large and small intestine, female reproductive system and pancreas. Also, clinical trials are investigating the use of ILT in the treatment of certain types of brain tumors and pelvic sarcomas in adults.
• Prophylactic cranial irradiation (PRI) This is external irradiation of the brain in case of risk of metastasis of the primary cancer (for example, lung) to the brain.

• Internal RT (brachytherapy): The radiation source is located near or in the tumor itself. The radiation source is usually placed in the implant. Implants can be in the form of wires, catheters (tubes), capsules or granules. The implant is placed directly into the body. For internal RT, you may need to go to hospital.

Internal radiation is usually delivered in one of 2 ways, described below. In both cases, implants are used.

• Interstitial RT: the source is implanted near or into the tumor. Used to treat head and neck, prostate, cervical, ovarian, breast, perianal and pelvic cancers.
• Intracavitary or intraluminal RT: the source is introduced into the body. Widely used in the treatment of uterine cancer. Researchers are also studying the use of these types of RT to treat breast, bronchial, cervical, gallbladder, oral, rectal, tracheal, and vaginal cancers.

• System LT: Radioactive substances such as iodine-131 and strontium-89 are used. The drugs are taken orally or injected. Used to treat thyroid cancer and non-Hodgkin's lymphoma in adults. Researchers are studying the use of this type of therapy to treat other forms of cancer.

How does a doctor determine the radiation dose?

The amount of radiation absorbed by tissues is called radiation dose. Until 1985 the dose was measured in rads (the dose of absorbed radiation). Now this unit is Gray. 1 Gray=100 rad. 1 centiGray (cGy) = 1 rad.
Different tissues tolerate different amounts of radiation. For example, the liver can withstand 3000 cGy, and the kidneys only 1800 cGy. The total dose is usually divided into smaller doses (fractions), which are irradiated every day for a certain time. This enhances the destruction of cancer cells while reducing damage to normal tissue.
The doctor works with a chart - the therapeutic coefficient. This ratio compares damage to cancerous and normal cells. Methods are available to increase damage to cancer cells and decrease damage to normal cells.

What is the energy source for external RT?

The sources are radioactive isotopes of iodine-125, -131, strontium-89, phosphorus, palladium, cesium, iridium, phosphate or cobalt. Other isotopes are still being studied.

Energy can be supplied as follows:

• X-rays or gamma rays, both are forms of electromagnetic radiation. Although they are formed in different ways, they all use photons.
• X-rays are created by devices - linear accelerators. Depending on the amount of energy in X-rays, X-rays can be used to kill cancer cells on the surface of the body (low energy level) and in deeper structures (high energy level). Compared to other types of radiation, X-rays can irradiate a fairly large area.
• Gamma rays are produced when isotopes of certain elements (iridium and cobalt 60) release radiant energy as they decay. Each element decays at a specific rate and each releases a different amount of energy, which determines the depth of penetration into the body (gamma radiation produced by the decay of cobalt-60 is used in the Gamma Knife treatment).
• Particle beams: Subatomic particles are used instead of photons. Particle beams are generated by linear accelerators, synchrotrons and cyclotrons. This treatment uses electrons generated by X-ray tubes, neutrons generated by radioactive elements and special equipment. Heavy ions (protons and helium), γ-mesons (pions) are small negatively charged particles generated by accelerators and a system of magnets. Unlike X-rays and gamma rays, particle beams do not penetrate deeply into tissue, so they are often used to treat superficial tumors and tumors under the skin.

Proton beam therapy is a type of particle beam therapy. Protons have energy in a very small region - the Bragg maximum. It can be used to treat tumors with high doses with little damage to adjacent normal tissue. So far it is rarely used. Research is currently underway on the use of such therapy in the treatment of intraocular melanoma, retinoblastoma, rhabdomyosarcoma, prostate, lung and brain cancer.

What is stereotactic radiosurgery and stereotactic radiotherapy?

Stereotactic radiosurgery uses a large dose of radiation to destroy brain tumors. And this is not surgery in the known sense. The patient's head is placed in a special frame attached to his own skull. The frame is needed to ensure that the particle beams follow exactly to the tumor. The dose and area of ​​irradiation are adjusted very precisely. Most adjacent structures are not damaged during the procedure.
Stereotactic surgery is performed in different ways. In the most common technique, a linear accelerator directs high-energy proton radiation into the tumor (linac radiosurgery). Gamma Knife, the second most common method, propagates radiation using cobalt-60. Finally, they can use heavily charged particle beams to direct radiation into the tumor.
Stereotactic radiosurgery is used primarily to treat small benign and malignant brain tumors (including meningiomas, acoustic schwannomas, and pituitary cancer). It is also used in the treatment of Parkinson's disease and epilepsy. It can be added that stereotactic radiosurgery is used to treat metastatic brain tumors.
Stereotactic radiotherapy uses the same principles as radiosurgery of the same name to distribute radiation into the tumor. However, stereotactic therapy uses small fractions of radiation rather than one large dose of radiation. This approach improves outcomes and minimizes side effects. This therapy is used in the treatment of both brain tumors and other localizations.
Clinical trials are studying the effectiveness of stereotactic radiosurgery and radiotherapy alone and in combination with other types of radiation therapy.

What other methods are being used or studied to increase the effectiveness of external RT?

The following techniques are used and studied:

• Three-dimensional (3D) conformal RT. Typically, the irradiation scheme is carried out in 2 dimensions. With three-dimensional conformal radiation, using a computer, it is possible to more specifically target the radiation to the tumor. Many radiation oncologists use this technique. A three-dimensional image of the tumor can be obtained using CT (computed tomography), MRI (magnetic resonance imaging), PET (positron emission tomography). Based on the image, computer programs distribute radiation to “fit” the shape of the tumor. Because adjacent healthy tissues are practically not damaged; larger doses can be used. Improved treatment results for cancers of the nasopharynx, prostate, lung, liver and brain have been described.
• Intensity modulated RT (IMRT, IMRT). This is a new type of three-dimensional conformal radiation therapy that uses beams of radiation (usually X-rays) of different intensities to deliver different doses of radiation to small areas of the body at one time. The technology makes it possible to irradiate the tumor with higher doses and cause less damage to adjacent normal tissue. In some cases, it is possible to irradiate the patient with high doses every day in this way, i.e. reducing treatment time and improving treatment results. There may also be fewer side effects.

The radiation comes from a linear accelerator equipped with a multi-leaf collimator (necessary for generating radiation). The equipment can rotate around the patient, i.e. radiation beams can be directed at better angles. The beams are perfectly adjusted to the shape of the tumor.
This new technology is used to treat tumors of the brain, head and neck, nasopharynx, breast, liver, lung, prostate and uterus. Long-term results of treatment will soon be known.

What is low and high energy transfer irradiation?

Linear energy transfer (LET) is the rate at which a type of radiation stores energy as it passes through tissue. High levels of stored energy kill more cells. Different types of radiation have their own LET levels. For example, X-rays, gamma rays, and electrons have low energy transfer, while neutrons, heavy ions, and pions have high energy transfer.
Who plans and distributes RT to patients?
Radiation therapy is carried out by a team consisting of a radiation oncologist, a dosimetrist, a biotechnician and a radiation therapist. Often RT is only part of a patient's treatment regimen. RT is often combined with chemotherapy.
The radiation oncologist also interacts with the pediatric oncologist, surgeon, radiation specialist, pathologist and other specialists to develop the ideal management plan for the patient.

What is treatment planning and why is it important?

Because There are many types of radiation and many ways of exposure, treatment planning is an important first step in treatment. Before starting radiation therapy, doctors specializing in radiation therapy will determine the amount and type of radiation.
If a patient is scheduled for external beam radiation, the radiation oncologist uses a simulation process to determine the area to be treated. During the simulation, the patient lies quietly on the table, and the doctor in a special X-ray unit determines the exact area (port) of radiation. In most patients, several ports are identified. During the simulation, CT or other imaging modalities may also be performed to determine the direction of radiation.
The areas to be irradiated are marked with temporary or permanent markers, indicating where to direct the radiation.
Depending on the type of RT, the patient may be offered special corsets to fix, for example, the head in order to eliminate its movements during the procedure. In some cases, special protective shields that are impenetrable to radiation are used to protect adjacent tissue.
At the end of the simulation, the RT team determines the radiation dose, how to deliver it, and how many cycles the patient will need.

What are radiosensitizers and radioprotectors?

Radiosensitizers and radioprotectors are chemical substances that modify the cell's response to radiation. Radiosensitizers are drugs that make cancer cells more sensitive to radiation. The ability of some substances to be radiosensitizers is being studied. Also, some anticancer drugs, such as 5-fluorouracil and cisplatin, also make cancer cells more sensitive to radiation.
Radioprotectors are drugs that protect normal cells from radiation. These drugs stimulate the “repair” of normal cells. Currently, such a drug is amifostine (Ethyol®). Other drugs are being studied.
What are radiopharmaceuticals (RPs)? How are they used?
Radiopharmaceuticals or radionuclides are radioactive drugs for the treatment of cancer, including thyroid and breast cancer; and pain relief from bone metastases. The most commonly used are samarium-153 (Quadramet®) and strontium-89 (Metastron™). These drugs eliminate pain from bone metastases. Both are administered intravenously in an outpatient setting and are sometimes combined with external RT. Other drugs are used less frequently - phosphorus-32, rhodium-186, gallium nitrate. Other radiopharmaceuticals are still being studied.

Internal radiation therapy (brachytherapy)

A doctor may decide that a high dose of radiation delivered to a small area of ​​the body is the best way to treat cancer. Internal radiation therapy allows the doctor to use a higher dose in a shorter time, unlike external radiation.
Internal radiation therapy places a radioactive source as close to the cancer cells as possible. Instead of using a large radiation machine, radioactive material placed in a thin wire, catheter, or tube (implant) is placed directly into the affected tissue. This treatment concentrates radiation on cancer cells and reduces radiation damage near nearby normal tissue. Radioactive materials used: cesium, iridium, iodine, phosphorus and palladium.
Internal radiation therapy can be used to treat cancers of the head and neck, breast, uterus, thyroid, cervix and prostate. The doctor can combine internal and external irradiation.
In this section, internal radiation therapy refers to implanted radiation, which is preferably referred to as “brachytherapy.” You can also hear from doctors interstitial irradiation or intracavitary irradiation, each form is a type of internal radiation therapy. Sometimes radioactive implants are called capsules or beads.
How is an implant placed in the body?
The type of implant and how it is inserted depend on the size and location of the tumor. Implants can be placed directly into the tumor (interstitial irradiation), in special applicators into the body cavity (intracavity irradiation) or canal (intraluminal irradiation); on the surface of the tumor; or to the area from which the tumor was removed. The implants may be removed soon or left in place for a longer period of time. If the implant must be left in place, the radioactive substance will soon lose radioactivity and soon become non-radioactive.
In interstitial irradiation, a radioactive source is injected into the tumor in a catheter, beads, or capsules. In intracavitary irradiation, a container or applicator containing a radioactive source is placed into a body cavity, such as the uterus. In surface brachytherapy, a radioactive source is placed in a small holder and placed in or near the tumor. In intraluminal brachytherapy, a radioactive source is placed into a channel of the body (such as the bronchus or esophagus).
Internal irradiation can also be done by injecting a solution into the bloodstream or body cavity. This method may be called unsealed internal radiation therapy.
Most types of implants only need to be used in a hospital setting. General or local anesthesia is given, i.e. You will not feel pain when the doctor inserts the implant.
How are other people protected from radiation when the implant is in place?
Sometimes a radioactive source in the implant emits high-energy beams outward. To protect others from radiation, you will be in a private room. Although nurses and other people caring for you may not spend much time in your room, they will provide the care you need. You should call a nurse if necessary, but be aware that the nurse will work faster and talk to you from the doorway more often than at the bedside. In most cases, your urine and feces will not be radioactive unless you are given unsealed internal radiation therapy.
The number of visitors will also be limited while you have the implant in place. Children under 18 years of age and pregnant women should not visit patients receiving internal radiation therapy. Make sure you tell visitors to check with hospital staff for any special instructions before entering the room. Visitors must sit at least 6*30.48 cm (6 feet) from the bed, and hospital staff will decide how much time visitors can spend. The time can vary from 30 minutes to several hours a day. Some hospitals use lead screens at the bedside.
What are the side effects of internal radiation therapy?
Side effects vary depending on the area of ​​the body. You are unlikely to have severe pain or severe illness. However, if the applicator is holding the implant, it may be somewhat uncomfortable. If you need it, your doctor will prescribe medications for pain and relaxation. If general anesthesia was used when the implant was placed, you may experience lethargy, weakness or nausea, but these symptoms will soon subside. If necessary, medications are used to eliminate nausea. Tell the nurse about any symptoms that are bothering you.

How long does the implant stay?
The doctor will decide how long the implant will remain in the body. This depends on the dose of radioactivity required for effective treatment. Your treatment regimen depends on the type of cancer, its location, your overall health, and other cancer treatment regimens you are receiving. Depending on where the implant is placed, you may have to keep it from moving by staying in bed. Temporary implants may have low or high dose rates. Implants with a low dose rate are left in place for several days, while implants with a high dose rate are removed after a few minutes. In some places where cancer is located, the implant remains for a long time. If you have a long-term implant, you may need to stay in a separate room for several days. The implant becomes less radioactive every day; By the time you are discharged, the radiation in your body will have weakened significantly. Your doctor will tell you if there are any special precautions you should take at home
What happens after implant removal?
No anesthesia is usually required when removing a temporary implant. In most cases, they are pulled out in the ward. When the implant is removed, the radioactivity in the body disappears. Hospital staff and visitors no longer have restrictions on being with you.
Your doctor will tell you whether you need to limit your activities after you are discharged. Most patients are allowed to do as much as they want. You may need extra time to sleep and rest, but you will soon be stronger.
The area where the implant was placed may be tender or painful for a while. If certain activities, such as sports or sexual intercourse, irritate the area, your doctor may advise you to temporarily limit the activity.
Remote brachytherapy
In remote brachytherapy, a computer sends a radioactive source through a tube into a catheter located near the tumor. The procedure is managed by a team of brachytherapy specialists who monitor the patient on a screen and communicate via a two-way communication system. The radiation remains in the tumor for only a few minutes. In some cases, several sessions of remote brachytherapy are required.
Remote brachytherapy can be used for low dose rate treatment regimens in hospital settings. Remote high-dose rate brachytherapy allows internal radiation therapy to be delivered on an outpatient basis. High dose rate treatment takes only a few minutes. Because The radioactive material does not remain in the body, the patient can return home after treatment. Remote brachytherapy is used for cancers of the cervix, breast, lung, pancreas, prostate and esophagus.

What new approaches to RT exist?

The combined use of hyperthermia (high temperatures) with RT is being studied. Scientists have found that with this combination, the tumor responds better to treatment.
Researchers are also studying radiolabeled antibodies to deliver radiation directly to tumors (radioimmunotherapy). Antibodies are highly specific proteins formed in the body in response to the appearance of antigens (foreign substances recognized by the immune system). Some tumor cells have specific antigens that trigger the production of tumor-specific antibodies. Large quantities of these antibodies can be produced in the laboratory and then radiolabeled. When introduced into the body, antibodies search for cancer cells that are destroyed by radiation. This approach minimizes the risk of damage to adjacent healthy tissue.
The following drugs have been developed: ibritumomab tiuxetan (Zevalin®) and iodine-131 tositumomab (Bexxar®), which are used to treat advanced adult non-Hodgkin lymphoma. Clinical trials are studying the treatment of such drugs for liver, lung, brain, prostate, thyroid, breast, ovarian, pancreatic, colorectal and leukemia cancers. Other drugs discovered include gefitinib (Iressa®) and imatinib mesylate (Gleevec®).

Diet during radiation therapy

Drink 8-12 cups of fluid per day. Drinks with high sugar content should be diluted with water.

Eat more often and in small portions. For example, it is better to eat 5 or 6 small meals a day than to eat 3 meals a day and eat more.

Eat easily digestible foods (foods low in fiber, fat and lactose).

Continue a low-fat, low-lactose, and low-fiber diet for 2 weeks after finishing radiation therapy. Gradually introduce new foods into your diet. You can start with small portions of low-fiber foods, such as rice, bananas, apple juice, mashed potatoes, low-fat cheese, and bread.

Avoid:
o Milk and dairy products (ice cream, sour cream, cheese)
o Spicy food
o Foods and drinks with caffeine (coffee, black tea and chocolate)
o Foods or liquids that cause gas (legumes, cabbage, broccoli, soy products)
o High fiber foods (raw vegetables and fruits, legumes, cereal and grain products)
o Fried and fatty foods
o Fast food establishments

Source : National Cancer Institute, National Institutes of Health www.health.mail.ru www.oncology.ru

Radiation therapy (radiotherapy) is treatment with ionizing radiation. It is used mainly to target tumors in order to cure the patient (radical radiation therapy) or temporarily alleviate his condition (palliative radiation therapy). Radiation therapy can be used for some non-tumor diseases (inflammatory, processes such as mastitis, hidradenitis, etc., eczema, neurodermatitis, etc.) in cases where other treatment methods have been unsuccessful.

Sources of ionizing radiation are radioactive isotopes (see), used in the form of specially manufactured preparations (see), or radiation generated by devices (see...,). Natural radioactive elements (radium-mesothorium) are currently no longer used for therapeutic purposes (radium therapy).

Radiation therapy for tumor diseases is based on a well-known pattern, which indicates that healthy and tumor tissues are not the same (see). Due to, as a rule, greater radiosensitivity, tumors are more damaged by radiation exposure than the surrounding healthy tissues, which inevitably fall into the irradiation zone. The greater the interval in the radiosensitivity of healthy and tumor tissues (therapeutic interval), the easier it is to destroy the tumor by irradiation, without causing significant harm to healthy surrounding tissues. Naturally, tumors that are highly radiosensitive expand the therapeutic interval. A therapeutic interval sufficient for treatment, as a rule, occurs for cervical cancer, tumors of the tonsils, pharynx, nasopharynx, larynx and some other organs. Radiation therapy can be used as an independent method of treatment (for example, for nasopharyngeal tumors, cancer, etc.). Most often, radiation therapy is carried out in combination with surgical treatment or chemotherapy (combined radiation therapy). With combined radiation and surgical treatment methods, radiation therapy can be used both in the preoperative (preoperative radiation therapy) and postoperative (postoperative, or prophylactic, radiation therapy) periods. Irradiation of a tumor is carried out mainly to suppress its activity; in cases where it is not possible to remove the tumor while maintaining the principle of ablastics (see), the main goal of radiation therapy is an attempt to bring the patient to an operable state. When carrying out pre- and postoperative radiation therapy, not only the tumor or its host, but also areas of possible metastasis are exposed to radiation. For example, with additional irradiation, the armpits, supraclavicular and subclavian areas are irradiated.

There are the following methods of radiation therapy: application, internal, intracavitary, interstitial, external.

Application radiotherapy- treatment with β- or γ-active drugs located on special applicators that hold radioactive sources in a certain place and at the required distance from the body surface. It is carried out to treat diseases of the skin or mucous membranes. Applicators in the form of moulages, which were previously used very widely, are now rarely used. More often, so-called flexible β-applicators are used, intended for the treatment of superficial diseases - neurodermatitis, capillary, etc. They are made in the form of a flexible plastic plate containing evenly distributed radioactive, or, which is applied to the affected skin for several minutes or even hours. When working with β-applicators, it is necessary to carefully monitor the safety of the plastic bag in which the applicator is located, since otherwise the patient’s skin may be contaminated with dust particles of radioactive drugs.

Internal radiation therapy carried out by introducing into the body (per os or directly into the bloodstream) radioactive drugs - most often I 131 (see Iodine, radioactive), P 32 (see), Au 148 (see Gold, radioactive). Used for blood diseases (for example, leukemia), lymphogranulomatosis. Patients receiving radioactive drugs orally require isolation in special wards; their urine is collected in special containers within 10 days after taking the drug (see Radioisotope Containers).

Intracavitary radiotherapy- irradiation of tumors of the abdominal organs by introducing radioactive drugs to them, most often cobalt-60 (see Cobalt, radioactive). Most often used in the treatment of cancer of the cervix and uterine cavity, bladder, and nasopharynx. The drugs are administered for several hours or even a day. Administration is carried out only in specially equipped rooms - radiomanipulation rooms. When administering drugs, personnel are behind special lead screens.

Patients with radioactive drugs are kept in special wards (see Radiology department). A special feature of the treatment is careful monitoring and prevention of drug loss. After the medications are removed, patients can stay in general wards.

Interstitial radiotherapy- irradiation of tumors by inserting radioactive cobalt needles into them or suturing the tumor with nylon threads filled with thin pieces of wire made of radioactive cobalt, gold or iridium. Most often used for superficial tumors, as well as tumors of the tongue and oral cavity. Radioactive needles and threads are inserted for several days and then removed. Recently, instead of needles and threads, colloidal solutions of radioactive gold-198 or very small iridium grains are injected into tumors. The introduction of grains is carried out using a special pistol, and colloidal solutions - using syringes in protective lead cases (see Radiological instruments).

External beam radiotherapy- irradiation using special installations that generate ionizing radiation, and the radiation source is located at some distance from the patient. The source of radiation can be an X-ray machine -; radioactive cobalt or cesium - telegammatherapy; betatron or linear accelerator - megavoltage therapy. Depending on what type of betatron radiation is used - electronic (see Electronic radiation) or bremsstrahlung, megavoltage therapy is distinguished between electronic and bremsstrahlung radiation. External beam radiation therapy is the most common type of radiation therapy. It is carried out only in special treatment rooms, where radiation sources are installed permanently (see Gamma devices). When using Luch and Rokus devices, which are characterized by good protection of the radiation source, the danger of radiation exposure for personnel is very insignificant.

Radiation therapy [synonym: curitherapy, radiumtherapy, radiotherapy (outdated names)] is a method of treating diseases using various types of ionizing radiation of different energies.

As a clinical discipline, radiation therapy is closely related to radiobiology (see), physics of radiation and dosimetry (see), as well as to the technique of therapeutic use of radiation sources; Its main sections are the methods of therapeutic use of radiation and the radiological clinic.

Radiation therapy combines the therapeutic use of x-ray, gamma, electron, proton, neutron and other ionizing radiation (see Alpha therapy, Beta therapy, Gamma therapy, Neutron therapy, Proton therapy, X-ray therapy, Electron therapy).

The rational organization of radiation therapy involves the concentration of its various types within large centralized hospital (clinical) institutions.

Radiation therapy should be carried out comprehensively; the success of treatment depends on this. Radiation therapy is carried out through the friendly work of radiologists and medical physicists, who jointly solve fundamental and particular clinical problems of optimal radiation exposure.

Objectives of radiation therapy: 1) dosimetric characteristics of radiation, assessment of dose fields created in lesions and healthy tissues; 2) radiobiological substantiation of radiation exposure, characteristics of tissue radiosensitivity, directional changes in radiosensitivity; 3) elucidation of the reactions of healthy and pathological tissues and the whole organism to irradiation, development of methods and tactics of irradiation, combating immediate and late complications.

A method of radiation therapy in which a radioactive substance is located inside the tumor tissue during treatment is called interstitial. Depending on the radiation used, a distinction is made between gamma therapy and β-therapy.

Interstitial gamma therapy is indicated for well-defined small tumors, the volume of which can be determined quite accurately. It is especially advisable to use interstitial treatment for tumors of mobile organs (cancer of the lower lip, tongue, breast, external genitalia) or for tumors requiring local irradiation (cancer of the inner corner of the eye, eyelid). To carry out interstitial gamma therapy, radioactive gamma-emitting preparations Ra, Co, Cs are used in the form of needles, pieces of wire, cylinders or granules. The needles have a stainless steel sheath that serves as a filter; the outer diameter of the needle is 1.8 mm. The introduction of radioactive needles into the tumor tissue is carried out in the operating room with mandatory observance of the rules of asepsis and antisepsis, as well as the protection of personnel from radiation. Local anesthesia of the tissues around the tumor is required; novocaine is not injected into the tumor tissue. The needle is inserted using special instruments, immersed into the eye, and fixed to the skin with a thread inserted into the eye. During the entire time of interstitial irradiation, the patient is in a special active ward. Once the required focal dose is reached, the radioactive needles are removed by pulling the threads.

Interstitial gamma needle therapy is not without its drawbacks. In addition to the traumatic nature of this procedure, a necrotic channel appears in the tissues around the needle due to the high dose, as a result of which the radiation source can shift and even fall out. Improvement and the search for new forms of drugs have led to the use of radioactive cobalt granules in nylon tubes for interstitial gamma therapy. Nylon tubes have a smaller outer diameter, minimally injure surrounding tissues and significantly reduce the time of personnel contact with the radioactive substance. Due to its flexibility and elasticity, the radiation source can be shaped to approximate the tumor configuration.

With interstitial gamma therapy, the optimal dose in time, i.e. the dose rate is 35-40 rad/hour. This dose rate allows 6000-6500 rads to be delivered to the tumor in 6-7 days. and cause radical damage to the tumor.

A type of interstitial irradiation is radiosurgical method. The essence of the method is to create access to the tumor and expose it to radioactive drugs or irradiate the tumor bed with radioactive substances after its removal. The radiosurgical method can be used for various localizations of the tumor process of stages I and II, as well as for tumors that are on the border of inoperability, but without the presence of distant metastases. This method is indicated for metastases of cancer of the oral cavity, lip, larynx, submandibular and cervical lymph nodes, soft tissue sarcomas, and cancer of the external genitalia.

In the radiosurgical treatment method, both gamma and β emitters are used. The form of the radioactive drug can be very diverse. Needles, nylon tubes with cobalt granules, Au granules, tantalum wire, colloidal radioactive solutions, as well as absorbable threads impregnated with them are used.

Method of administering a colloidal solution of Au 198 for intradermal metastases

When treating some inflammatory processes and malignant neoplasms of the skin and mucous membrane, radioactive drugs can be placed either directly on the surface of the pathological focus, or at a distance of no more than 0.5-1.5 cm. This method of irradiation is called application Depending on the size and depth of the lesion, gamma-emitting radioactive drugs are used.

Application β-therapy used in the treatment of processes spreading in the superficial layers (up to 4 mm) of the skin and mucous membrane (capillary angiomas, hyperkeratoses, leukoplakia, neurodermatitis, erosions). β-radiation P, intrium, waist, promethium, strontium, xenon act on the pathological focus without irradiating the underlying tissue. Plates of various sizes with a radioactive substance with a thickness of 0.1 mm to 0.35 mm are covered with a thin polyethylene or thermene film.

Treatment of patients with capillary angiomas is carried out in the form of a course consisting of 6-9 daily radiation sessions. The daily dose is 300-500 rads, and the total dose for the entire course is 2000-3000 rads. Treatment results in children are usually better than in adults. For eczema, β-application therapy is used only when other methods do not produce an effect. As a result of treatment, the inflammatory process and skin infiltration usually decrease, the itching weakens and disappears.

Application gamma therapy used in cases where the process is located at a depth of more than 4 mm and is indicated for tumors of the skin and mucous membrane, relapses and metastases in the skin and subcutaneous tissue. During application gamma therapy, radioactive drugs are placed in special dummies that simulate the shape of the irradiated surface. The dummy is made from a mixture of wax and paraffin. A plate of this mass, 0.5-1.0 cm thick, is heated in hot water (up to 40 0) and when it becomes soft, it is applied to the surface to be irradiated. To ensure that the radiation surface exactly matches the pathological focus, it is outlined in magenta, after which an imprint of the contours of the area to be irradiated is left on the dummy. Radioactive drugs are placed inside this circuit. To obtain a uniform dose field, it is necessary to follow certain rules for the location of drugs. More often, preparations are placed in the form of a rectangle or circle, but always in such a way that the irradiation area exceeds the visible dimensions of the pathological focus. Application gamma therapy can be carried out by continuous or fractionated irradiation.

Finally, it is necessary to note another method of radiation therapy, based on the selective absorption of certain radioactive drugs by tissues or organs, called internal exposure. Radioactive drugs are administered per.os, intravenously, intra-arterially.

Internal irradiation method

Currently, colloidal solutions of P, J, and Au are used for intra-arterial therapy.

Radioactive Au 198 is used in the treatment of leukemia. The colloidal solution is administered intravenously at the rate of 0.5-1 microcuries per 1 kg of patient weight, with a total dose of 5 microcuries. If necessary, a second course is carried out after 4-6 months, and 1/2 or 1/3 of the initial dose is administered.

Radioactive J 131 is used mainly for stage II and III hyperthyroidism, tumor relapses after surgery, for thyroid cancer as an independent method of treatment, as well as for prophylactic purposes as pre- and postoperative treatment. Internal exposure is rad. J is limited to the effect of ionizing radiation on hyperplastic thyroid cells without damaging surrounding organs and tissues. When treating thyrotoxicosis, the patient should exclude foods containing iodine from food for 1.5-2 months and not take iodine preparations. The dose of radioactive drugs depends on the degree of hyperfunction of the thyroid gland. The amount of J required for treatment can be applied simultaneously or in fractional doses of 1.5-2 microcuries. For thyroid cancer, in order to reduce the mitotic activity of cells, 30-45 microcuries are prescribed 2-3 weeks before surgery. After radical surgery in the early stages, J 131 is prescribed at a dose of 5 microcuries every three weeks up to a total dose of 50-100 microcuries. For inoperable thyroid cancer, 50-60 microcuries of J are administered every 2-3 weeks until a therapeutic effect is obtained.

Each of the considered methods of radiation therapy has its own advantages and disadvantages. Thus, remote irradiation does not fully provide the ratio of absorbed doses. Even under seemingly favorable conditions, a large volume of healthy tissue is irradiated, the regenerative capacity of which is significantly reduced.

Contact irradiation methods create a more favorable dose ratio. However, for tumors that spread to a greater depth than 1 cm, the use of contact methods will be ineffective. Therefore, for more rational irradiation it is necessary to combine remote irradiation with one of the contact methods. This method of treatment is called combined method radiation therapy.

In respect of combination treatment radiation therapy may be combined with surgical intervention, chemotherapy, or both. The sequence of its use depends on the stage of the disease, the clinical form of the tumor, its location and the general condition of the patient. Radiation therapy can be carried out in various versions of remote, intracavitary, interstitial irradiation with electrocoagulation, resection or extirpation of the affected organ.

Hence, the following methods of radiation therapy are distinguished:

· Self-administered radiation therapy – radiation or chemotherapy;

· Combined radiation therapy – remote irradiation with irradiation using one of the contact methods;

· Combined radiation therapy - radiation therapy with surgical method;

· Complex radiation therapy - radiation and chemotherapy.

Radiotherapy planning

n The results of scientific research make it possible to plan doses and the number of fractions at which the tolerance level of normal tissues will not be exceeded;

n Apply different fractionation modes;

n Strengthen the effect of ionizing radiation on the tumor;

n Protect surrounding tissue

During the interview, they find out whether the patient has undergone past radiation treatment. If it took place, then you should find out all the details (when and by what method the radiation therapy was performed, which parts of the body were irradiated, in what total dose, what complications were observed).

Can't be relied upon only for a patient’s message - an extract from the medical history or a written certificate from the medical institution where he was treated is required.

This is extremely important, because when treating tumors, a second course of radiation can be carried out only after 60-70 days after the end of the first and taking into account the conditions of the previous irradiation.

However, it was already noted above that the effectiveness of repeated courses is low. The first course should be as radical as possible and, if possible, the only one

Based on the results of a comprehensive examination of the patient, the oncologist, radiation therapist (and often the therapist and hematologist) develop a coordinated treatment strategy. It depends on the location of the tumor, its size, histological nature and stage of development.

Small tumor can be cured with both surgery and radiation therapy.

In this case, the choice of method depends primarily on the location of the tumor and the possible cosmetic consequences of the intervention.

In addition, it must be taken into account that tumors emanating from different anatomical areas differ in their biological characteristics.

Tumors amenable to radical treatment (radiocurable tumors) include: cancer of the skin, lips, nasopharynx, larynx, breast, as well as retinoblastoma, medulloblastoma, seminomas, ovarian dysgerminomas, localized lymphomas and lymphogranulomatosis.

Radiation destruction large tumor encounters almost insurmountable difficulties due to radiation damage to its vessels and stroma, resulting in radiation necrosis.

In such cases, they resort to combined treatment. The combination of radiation exposure and surgery gives good results for Wilms tumor and neuroblastomas in children, cancer of the sigmoid and rectum (so-called colorectal cancer), embryonal testicular cancer, rhabdomyosarcomas, and soft tissue sarcomas.

Surgery is very important to remove the remaining tumor after radiation therapy.

At the same time, radiation therapy is indicated for relapse of a cancer tumor after surgical or combined treatment (recurrence of cancer of the skin, lower lip, cervix), as well as for local metastases in the lymph nodes, bones, and lungs.

Pre-radiation period

IN pre-radiation period prepare the patient for treatment.

It should begin with psychological preparation. The patient is explained the need for radiation exposure, its effectiveness, possible changes in well-being and some radiation reactions, features of the regime and nutrition are indicated. A conversation with the patient should instill in him hope and confidence in good treatment results.

Further stages of preparation are enhanced nutrition with the consumption of large amounts of fluid, saturation of the body with vitamins (in particular, at least 1 g of vitamin C per day), sanitation of irradiated surfaces and cavities.

n In areas to be irradiated, the skin should be clean, without abrasions or pustules.

n All physiotherapeutic procedures and medications for external use such as ointments and mash are cancelled.

n When irradiating the facial part of the head, the oral cavity is sanitized.

n Drinking alcohol and smoking are prohibited. In case of concomitant inflammatory process, antibiotics are prescribed, in case of anemia - means for its correction.

The next important step is clinical tonometry , described above. Here it is necessary to emphasize once again that in connection with the advent of computer and magnetic resonance imaging, fundamentally new possibilities are being created for extremely precise aiming of radiation beams at the target.

From the analysis of the location of the target on the plane, a transition is made to the volumetric perception of the tumor, from anatomical information - to geometric representations, to the construction of complex dosimetric distributions provided by computer programs

n Based on the results of clinical radiobiological analysis and topometry, such a type of radiation and such physical and technical conditions of irradiation are selected so that the intended amount of energy is absorbed in the tumor with a maximum dose reduction in the surrounding tissues.

In other words, the optimal total absorbed dose of radiation, a single dose (dose from each exposure), and the total duration of treatment are established.

Taking into account the topographic and anatomical features of the tumor and its histological structure, external contact or combined irradiation is chosen. The irradiation technology and the type of device (apparatus) to be used are determined.

The conditions for conducting the course are agreed with the attending physician - on an outpatient basis or in a hospital.

Together with a physicist engineer, the doctor, using a dosimetric plan, outlines the optimal distribution of fields for remote irradiation.

Static irradiation can be carried out through a single input field on the body surface (single-field irradiation) or through several fields (multifield irradiation). If the fields are located above the irradiated area from different sides so that the tumor is in the intersection of the radiation beams, we speak of multifield cross irradiation . This is the most common method. It allows you to significantly increase the focal dose compared to the dose in neighboring organs and tissues.

The main task of clinical topometry is to determine the volume of radiation based on accurate information about the location, size of the pathological focus, as well as surrounding healthy tissues and present all the data obtained in the form of an anatomical and topographic map (sections).

The map is performed in the cross-sectional plane of the patient's body at the level of the irradiated object.

On the section, the directions of radiation sources during external beam radiation therapy or the location of radiation sources during contact therapy are noted.

The choice of the number, location, shape and size of fields is strictly individual. It depends on the type and energy of radiation, the required single and total doses, the size of the tumor, and the size of the zone of its subclinical spread. The most commonly used are two opposing fields, three fields (one in front or behind and two on the side), four fields with beams intersecting at the hearth.

At mobile irradiation the radiation source moves relative to the patient. The three most common methods of mobile irradiation are: rotational, sectoral and tangent.

With all these methods, the radiation beam is aimed at the tumor.

Radiation therapy is carried out from two opposing shaped fields of complex configuration, if necessary, with the connection of a third additional field. The irradiation field includes a tumor, Mts in the lymph nodes (bronchopulmonary, root, upper and lower tracheal, paratracheal) or areas of their localization.

n After reaching the total focal dose of 45-50 Gy, it is recommended to reduce the irradiation fields and increase the radiation dose to 70-80 Gy

The pre-radiation period ends with the finalization of the treatment plan. A treatment plan is a set of clinical-radiobiological and clinical-dosimetric planning documents, including both a dose distribution map in the patient’s body and radiographs taken through the input fields and confirming the correct targeting of the radiation beams to the lesion.

n By the beginning of the radiation period it is necessary to carry out field marking exposure to the patient's body. To do this, the patient is given the position that he will occupy during therapeutic irradiation. Next, the radiation beam is aimed at the tumor (of course, the installation is not turned on and irradiation is not carried out).

When the patient is positioned on the table of the radiotherapy apparatus, laser centralizers or light fields of radiation sources are combined with marks on the surface of the body.

n The central axis of the beam must pass through the center of the input field and the center of the tumor, therefore aiming at the lesion during static irradiation is called centration.

When rotation Irradiation is carried out along the entire perimeter of the patient’s body. The advantage of the method is the concentration of the absorbed dose in the lesion with a simultaneous reduction of the dose in the surrounding tissues, especially in the skin. However, the integral absorbed dose in the patient's body turns out to be significant. Conventionally, we can consider that the rotational method is the extreme version of multifield cross irradiation, when the number of fields is extremely large. The method is indicated when the tumor is localized near the midline axis of the body (for example, esophageal cancer).

At sector irradiation the source moves relative to the patient’s body along arcs within the selected angle -90°, 120°, 180° (Fig. IV.8). This method is advisable to use when the tumor is eccentrically located in the patient’s body (for example, with lung or bladder cancer). At tangent During irradiation, the center of rotation of the system is located at a small depth below the surface of the body. Thus, the beam from the moving source is always directed tangentially relative to the irradiated part of the patient’s body. This is beneficial when irradiating a superficial lesion of sufficient extent (for example, when disseminating cancerous nodules in the skin of the chest wall after removal of the mammary gland).

Centering can be done using mechanical means: localizer tube, pointer arrows or rods connected to the radiation head. More convenient optical methods centering: the light beam is rejected by the mirror in the direction of the ionizing radiation beam and illuminates the field on the surface of the patient’s body. This light field is combined with a planned field marked on the skin and light “bunnies” directed perpendicular to it from additional centralizers.

In recent years, special devices have been created – simulators, which are designed to simulate all movements of the radiation source.

The simulator is an X-ray machine equipped with an X-ray image intensifier and a display for demonstrating the image. The tube can move in a circle around the patient.

Radiation period - the period of exposure to radiation under constant medical supervision of the patient. Clinical supervision of the patient during the radiation and post-radiation periods is extremely important, because allows you to modify the treatment plan and determine the necessary concomitant treatment.

n For irradiation of each field, the patient is given a comfortable position. Extremely important immobilization of the patient.

n Even a slight movement of it leads to a change in the dose distribution. Immobilization is carried out using various devices.

n To fix the head and neck, fixation devices made of thermoplastic material are used. It is softened in hot water and then modeled for the appropriate patient, after which the material quickly hardens.

n The correctness of beam targeting is checked using a simulator or radiography (in the latter case, radiopaque thin catheters or lead markers are placed at the edges of the intended field to obtain their image on the images).

n During the irradiation process, the doctor or laboratory assistant watches the patient on a TV screen.

n The intercom provides two-way communication between the doctor and the patient. At the end of the irradiation, the patient is prescribed to rest for 2 hours in the fresh air or in a room with good ventilation.

n Information about each exposure is recorded in the medical history.

Standard isodose maps show the distribution of absorbed energy in tissues, provided that the radiation beam is incident on the irradiated surface perpendicular to it. However, the real surface of the human body is rounded-convex in most areas.

In order to avoid distortion of the calculated dose distribution, compensators or boluses made of tissue-equivalent material (for example, paraffin) are used.

n Wedge filter allows you to change the dose distribution in tissues, since under the narrow part of the wedge the absorbed dose is noticeably higher than under the expanded part.

n For advanced tumors, uneven irradiation is sometimes performed using lattice filters. This filter is a lead plate with numerous holes. Radiation reaches only those areas of the body surface that are located under the holes. Under areas covered with lead, the dose is 3-4 times less and is due only to scattered radiation.

n When irradiating objects of irregular shape, it becomes necessary to use irradiation fields of complex configuration.

n Such "curly" fields can be obtained using lead or tungsten shielding blocks. They are placed on special stands that are attached to the radiation head of the device. For the same purpose, a shaped shielding diaphragm made of lead blocks is used.

n In this way, it is possible to protect organs that are especially sensitive to radiation: eyes, spinal cord, heart, gonads, etc., which may be close to the radiation zone.

n Sometimes a protective lead block is placed in the central part of the working beam. It seems to split the dose field into two halves. This is advisable, for example, when irradiating the lungs, when it is necessary to protect the spinal cord and heart from radiation.

Fractionated Irradiation is the main method of dose delivery for remote therapy. Irradiation is carried out in separate portions, or fractions.

Various dose fractionation schemes are used:

ü regular(classical) fine fractionation - 1.8-2.0 Gy depending on the histological type of tumor

ü Medium fractionation– 4.0-5.0 Gy per day 3 times a week;

ü Major fractionation-- 8.0-12.0 Gy per day 1-2 times a week;

ü Intensely concentrated irradiation – 4.0-5.0 daily for 5 days (for example, as preoperative preparation;

ü Accelerated fractionation – irradiation 2-3 times a day with regular fractions with a decrease in the total dose for the entire course of treatment;

ü Hyperfractionation, or multifractionation– splitting the daily dose into 2-3 fractions with a reduction in the dose per fraction to 1.0-1.5 Gy with an interval of 4-6 hours, while the duration of the course may not change, but the dose increases;

ü Dynamic Fractionation – irradiation with different fractionation schemes at individual stages of treatment;

ü split courses– irradiation regimen with a long break for 2-4 weeks in the middle of the course or after reaching a certain dose;

ü Low dose option of photon total body irradiation - from 0.1-0.2 to 1-2 Gy in total;

ü High-dose version of photon total body irradiation from 1-2 to 5-6 Gy in total;

ü Low-dose version of photon subtotal body irradiation - from 1-1.5 Gy to 5-6 Gy in total;

ü High-dose version of photon subtotal body irradiation from 1-3 to 18-20 Gy in total;

ü Electronic total or subtotal irradiation of the skin in various modes for tumor damage

ü The dose per fraction is more important than the total time of treatment. Large fractions are more effective than small ones. Enlargement of fractions while reducing their number requires a reduction in the total dose if the total course time does not change.

Thus, the main task when conducting irradiation sessions is to ensure accurate reproduction of the planned irradiation conditions at the therapeutic installation

Radiation therapy: pre- or postoperative irradiation, independent.

Indications for preoperative irradiation:

ü tumor size is more than 3 cm in diameter;

ü metastases;

ü fixation to the skin, skin ulceration;

ü rapid tumor growth

Target - reduce the volume of the tumor, transform it into an operable form, destroy proliferating tumor cells, reduce the likelihood of dissemination of tumor cells during surgery.

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Methods of intracavitary gamma therapy for cervical cancer

Intracavitary gamma therapy according to the generally accepted option

We previously presented a detailed description of these methods and treatment results in the monograph “Clinic and Treatment of Cervical Cancer” [Bohman Ya. V., 1976]. The generally accepted options for intracavitary gamma therapy involve the introduction into the uterine cavity and vagina of radionuclide sources of the linear form 60Co, the total activity of which is 0.91-1.82 MBq. The duration of an irradiation session with this method is 24-48 hours.

For uniform distribution of radiant energy in the pelvis, various models of colpostats have been proposed (G. Fletcher, V. P. Tobilevich, etc.). Their purpose is to fix radionuclides in a certain position. The intervals between intracavitary irradiation sessions are usually 5-7 days. Single absorbed doses at points A, depending on the stage of cervical cancer, are 10-15 Gy, at points B - 3-5 Gy, total at points A - 60-80 Gy, at points B - 12-18 Gy.

Calculation of absorbed doses during intracavitary gamma therapy is carried out on anatomical areas: the zone of the paracervical triangle (point A) and the lateral sections of the parametric tissue (point B). Points A are located at the intersection of the uterine artery and the ureter, in the upper part of the so-called paracervical triangle, which includes tissue near the cervix. They can occupy different positions in relation to the bone structures of the pelvis.

These counting points are determined at a distance of 2 cm from the sources introduced into the uterine cavity, and 2 cm above the lateral vault of the vagina. Points B correspond to the localization of the obturator lymph nodes, located at the same level as points A, but spaced 5 cm from the central axis of the small pelvis, regardless of the location of the uterus and the radiation sources introduced into it.

Subsequently, it was also proposed to carry out dosimetry at points V (posterior wall of the bladder in the area of ​​Lieto's triangle) and R (anterior wall of the rectum) in the projection of the internal os of the cervix. In recent years, new critical points have been introduced into the practice of clinical dosimetry. At point T, the absorbed dose is measured directly in the primary tumor: it is located 1 cm above the external os and 1 cm lateral to the linear source located in the cervical canal. Point C is the area of ​​the external iliac lymph nodes. Point D is located 1 cm above the end of the linear source in the uterine cavity.

Medical experience, careful study of the dynamics of tumor regression, and cytological studies during treatment are no less important in determining the optimal doses for each patient than their registration at recording points. As Fletcher wittily put it, “it’s the tumor that needs to be treated, not the alphabet.”

With intracavitary gamma therapy using the generally accepted method, the radiation dose to organs and tissues not affected by the tumor can be significant. Radionuclides injected into the uterus and vagina are usually not related to each other. Therefore, the possibility of their displacement during a long irradiation session (24–45 hours) leads to deformation of the dose field. This worsens the conditions for tumor irradiation and causes an increase in dose loads on the bladder and rectum.

Intracavitary gamma therapy based on the principle of manual sequential introduction of radionuclide sources

With the manual method of introducing radiation sources (simple afterloading), the first stage - preparatory - is carried out outside the zone of exposure to ionizing radiation and consists of introducing endostatic devices and fixing them relative to the tumor; X-ray control of the spatial placement of treatment tips and tonometric measurements; dosimetric preparation and choice of radiation program.

60Co preparations, intended for introduction into vaginal and uterine applicators, are mounted on metal rods with springs, allowing them to be rotated in the ovoid cavity. Radiation sources for the uterine applicator are placed in a nylon tube, their number is determined by the length of the uterine cavity and cervical canal.

Sessions of intracavitary gamma therapy are carried out once every 5-6 days. The cervical canal is expanded to the 5-6th number of the Hegar dilator and an inactive uterine and vaginal applicator is inserted. The colpostat system is fixed with a sterile tampon, which ensures a stable position of the colpostat and the greatest possible distance between the radiation sources, the rectum and the bladder.

The correct installation of the system is controlled by an X-ray examination carried out directly on the gynecological chair using an X-ray machine. The images are taken in two projections - frontal and sagittal. In this case, 3 colpostat tubes are filled with simulators of radioactive drugs, and the rectum and bladder are contrasted with rubber catheters.

A two-plane image of the colpostat helps determine radiation exposure to the primary tumor and adjacent organs. In 5% of cases, there is a need for appropriate correction of the installed system. It consists of changing the position of the ovoids or choosing a more appropriate number of source simulators introduced into the uterus.

Patients are transported to the ward after completion of the x-ray examination and confirmation of the correct placement of the inactive metracolpostat system. Radionuclide sources are introduced into the tube when the patient is already in bed with a bedside protective screen. The total activity of the nuclide in the radioactive source is 0.91-1.82 MBq. The duration of the irradiation session is 22-26 hours. Absorbed doses are calculated using X-ray data, taking into account the distance between the radiation source and dose recording points in the pelvis.

With the same activity of sources introduced into the uterus and vagina, the rectum is exposed to the greatest radiation from vaginal applicators. Single absorbed doses in the rectum vary between 5.5-7 Gy. In a number of observations they exceed 10 Gy. Timely detection of high dose values ​​in the bladder and rectum allows you to change the set and exposure of radionuclide drugs or change the ratio of activities of sources administered endocervically and endovaginally. This prevents severe radiation damage to organs adjacent to the cervix.

The immediate, immediate and long-term results of radiation treatment of 359 patients with cervical cancer were subjected to a comparative analysis, 153 of whom (group 1) were treated with a combined radiation method using intracavitary gamma therapy in the conventional version, 206 (group 2) were subjected to intracavitary gamma therapy. therapy based on the principle of manual sequential introduction of radioactive sources [Vishnevskaya E. E., 1983].

An assessment of the frequency and severity of early radiation reactions and complications observed in patients of the two analyzed groups did not reveal significant differences. However, the frequency of late erosive-desquamative and ulcerative rectitis in group 2 decreased by more than 4 times, catarrhal and ulcerative cystitis by 1.2 times, and radiation injuries such as recto- or vesicovaginal fistulas were not observed at all.

The 5-year survival rate of stage I cervical cancer patients treated using the principle of manual sequential introduction of low-level radiation sources was 95.7%, stage II - 75.1%, stage III - 58.5%. The survival rate with this method is significantly higher than for those treated with the generally accepted method of intracavitary gamma therapy, where it was 76.2, 65.5 and 39.2%, according to the stages.

Method of viutripavity gamma therapy using the AGAT-V device

A treatment session for patients with cervical cancer using the AGAT-V hose apparatus is preceded by the following procedures: introduction of metracolpostat and x-ray monitoring of the spatial placement of its elements; tonometric measurements and dosimetric determination of the duration of the irradiation session. Careful, precise installation and fixation of endostats, taking into account the individual characteristics of the patient and the tumor process, ensures the possibility of conducting an optimal radiation session and determines its success.

Radiation therapy: what it is and what the consequences are is a question that interests people facing cancer problems.

Radiation therapy in oncology has become a fairly effective means in the fight for human life and is widely used throughout the world. Medical centers providing such services are highly rated by specialists. Radiation therapy is carried out in Moscow and other Russian cities. Often this technology makes it possible to completely eliminate a malignant tumor, and in severe forms of the disease, prolong the patient’s life.

What is the essence of technology

Radiation therapy (or radiotherapy) is the exposure of ionizing radiation to tissue damage in order to suppress the activity of pathogenic cells. Such exposure can be carried out using x-rays, neutrons, gamma radiation or beta radiation. A directed beam of elementary particles is provided by special medical-type accelerators.

Radiation therapy does not directly destroy the cellular structure, but changes the DNA to stop cell division. The effect is aimed at breaking molecular bonds as a result of ionization and radiolysis of water. Malignant cells are distinguished by their ability to rapidly divide and are extremely active. As a result, it is these cells, as the most active ones, that are exposed to ionizing radiation, and normal cellular structures do not change.

Strengthening the impact is also achieved by using different directions of radiation, which makes it possible to create maximum doses in the affected area. This treatment is most widespread in the field of oncology, where it can act as an independent method or complement surgical and chemotherapy methods. For example, radiation therapy of the blood for various types of blood lesions, radiation therapy for breast cancer or radiation therapy to the head show very good results at the initial stage of the pathology and effectively destroy cell remnants after surgery at later stages. A particularly important area of ​​radiotherapy is the prevention of metastasis of cancer tumors.

This type of treatment is often used to combat other types of pathologies not related to oncology. Thus, radiotherapy shows high effectiveness in eliminating bone growths on the legs. X-ray therapy is widely used. In particular, such irradiation helps in the treatment of hypertrophied sweating.

Features of treatment

The main source of directed particle flow for performing medical tasks is a linear accelerator - radiation therapy is carried out with the appropriate equipment. The treatment technology involves immobilizing the patient in a supine position and smoothly moving the beam source along the marked lesion. This technique allows you to direct the flow of elementary particles at different angles and with different radiation doses, while all movements of the source are controlled by a computer according to a given program.

The radiation regimen, treatment regimen and course duration depend on the type, location and stage of the malignant neoplasm. As a rule, the course of treatment lasts 2-4 weeks with the procedure performed 3-5 days a week. The duration of the irradiation session itself is 12-25 minutes. In some cases, a one-time treatment is prescribed to relieve pain or other manifestations of advanced cancer.

Depending on the method of delivering the beam to the affected tissue, a distinction is made between superficial (remote) and interstitial (contact) effects. Remote irradiation involves placing beam sources on the surface of the body. In this case, the flow of particles is forced to pass through a layer of healthy cells and only after that focus on malignant formations. With this in mind, there are various side effects when using this method, but despite this, it is the most common.

The contact method is based on the introduction of a source into the body, specifically into the affected area. This option uses devices in the form of a needle, wire, or capsule. They can be inserted only for the duration of the procedure or implanted for a long time. With the contact method of exposure, a beam is directed strictly at the tumor, which reduces the effect on healthy cells. However, in terms of the degree of trauma, it is superior to the surface method, and also requires special equipment.

What types of rays can be used

Depending on the task assigned to radiation therapy, various types of ionizing radiation can be used:

1. Alpha radiation. In addition to the stream of alpha particles produced in a linear accelerator, various techniques are used based on the introduction of isotopes, which can be quite simply and quickly removed from the body. The most widely used are radon and thoron products, which have a short life span. Among the various techniques, the following stand out: radon baths, drinking water with radon isotopes, microenemas, inhaling aerosols saturated with isotopes, using bandages with radioactive impregnation. Thorium-based ointments and solutions are used. These treatment methods are used in the treatment of cardiovascular, neurogenic and endocrine pathologies. Contraindicated for tuberculosis and pregnant women.

2. Beta radiation. To obtain a directed flow of beta particles, appropriate isotopes are used, for example, isotopes of yttrium, phosphorus, and thallium. Beta radiation sources are effective with the contact method of exposure (intrastitial or intracavitary version), as well as with the application of radioactive applications. Thus, applicators can be used for capillary angiomas and a number of eye diseases. For contact effects on malignant formations, colloidal solutions based on radioactive isotopes of silver, gold and yttrium are used, as well as rods up to 5 mm long made from these isotopes. This method is most widely used in the treatment of oncology in the abdominal cavity and pleura.

3. Gamma radiation. This type of radiation therapy can be based on both the contact method and the remote method. In addition, a variant of intense radiation is used: the so-called gamma knife. The source of gamma particles is the cobalt isotope.

4. X-ray radiation. To carry out therapeutic effects, X-ray sources with a power of 12 to 220 keV are intended. Accordingly, with increasing emitter power, the depth of penetration of rays into tissues increases. X-ray sources with energies of 12-55 keV are aimed at working from short distances (up to 8 cm), and treatment covers the superficial skin and mucous layers. Long-distance therapy (distance up to 65 cm) is carried out by increasing the power to 150 -220 keV. Remote exposure of medium power is intended, as a rule, for pathologies not related to oncology.

5. Neutron radiation. The method is carried out using special neutron sources. A feature of such radiation is the ability to combine with atomic nuclei and the subsequent emission of quanta that have a biological effect. Neutron therapy can also be used in the form of remote and contact effects. This technology is considered the most promising in the treatment of extensive tumors of the head, neck, salivary glands, sarcoma, and tumors with active metastasis.

6. Proton radiation. This option is based on the remote influence of protons with energies up to 800 MeV (for which synchrophasotrons are used). The proton flux has a unique dose gradation based on penetration depth. This therapy makes it possible to treat very small lesions, which is important in ophthalmic oncology and neurosurgery.

7. Pi-meson technology. This method is the latest achievement in medicine. It is based on the radiation of negatively charged pi-mesons produced on unique equipment. This method has so far been mastered only in a few of the most developed countries.

What are the dangers of radiation exposure?

Radiation therapy, especially its remote form, leads to a number of side effects, which, given the danger of the underlying disease, are perceived as an inevitable but minor evil. The following characteristic effects of radiation therapy for cancer are highlighted:

1. When working with the head and neck area: it causes a feeling of heaviness in the head, hair loss, and hearing problems.
2. Procedures for the face and neck area: dry mouth, discomfort in the throat, pain when swallowing, loss of appetite, hoarseness in the voice.
3. Measures on the organs of the thoracic region: dry cough, shortness of breath, muscle pain and pain symptoms during swallowing movements.
4. Treatment in the breast area: swelling and pain in the gland, skin irritations, muscle pain, cough, throat problems.
5. Procedures on organs related to the abdominal cavity: weight loss, nausea, vomiting, diarrhea, pain in the abdominal area, loss of appetite.
6. Treatment of the pelvic organs: diarrhea, difficulty urinating, vaginal dryness, vaginal discharge, pain in the rectum, loss of appetite.

What to consider during treatment

As a rule, during radiation exposure, skin disorders are observed in the area of ​​contact with the emitter: dryness, peeling, redness, itching, rash in the form of small papules. To eliminate this phenomenon, external agents are recommended, for example, Panthenol aerosol. Many body reactions become less pronounced when nutrition is optimized. It is recommended to exclude hot seasonings, pickles, sour and rough foods from the diet. Emphasis should be placed on steamed foods, boiled foods, and chopped or pureed ingredients.

The diet should be frequent and fractional (small doses). It is necessary to increase fluid intake. To reduce the manifestations of problems in the throat, you can use a decoction of chamomile, calendula, and mint; instill sea buckthorn oil into the nasal sinuses, consume vegetable oil on an empty stomach (1-2 tablespoons).

During the course of radiation therapy, it is recommended to wear loose-fitting clothing, which will eliminate mechanical impact on the area where the radiation source is installed and rubbing of the skin. It is best to choose underwear from natural fabrics - linen or cotton. You should not use a Russian bath or sauna, and when swimming, the water should be at a comfortable temperature. You should also take care from prolonged exposure to direct sunlight.

What does radiation therapy do?

Of course, radiation therapy cannot guarantee a cure for cancer. However, timely application of its methods allows one to obtain significant positive results. Considering that radiation leads to a decrease in the level of leukocytes in the blood, people often wonder whether it is possible to get foci of secondary tumors after radiation therapy. Such phenomena are extremely rare. The real risk of secondary cancer occurs 18-22 years after irradiation. In general, radiation therapy can relieve a cancer patient from very severe pain in advanced stages; reduce the risk of metastasis; destroy residual abnormal cells after surgery; really overcome the disease in its early stages.

Radiation therapy is considered one of the most important ways to fight cancer. Modern technologies are widely used throughout the world, and the world's best clinics offer such services.