Radiation Therapy, Types, Indications, and Side Effects

Radiation Therapy

Radiation Therapy:

High doses of radiation are used in radiation therapy, also known as radiotherapy, as a cancer treatment to eradicate cancer cells and reduce tumor size. When taking x-rays of your teeth or broken bones, for example, radiation is used at low doses to see inside your body.

Emission Method:

The goal of radiation therapy is to destroy the cells that make up the pathological focus, such as a tumor. The primary cause of "death" of cells, which does not mean direct decay (see necrosis, apoptosis), but inactivation (cessation of division), is considered a violation of their DNA. Both directly and indirectly, through the radiolysis of water, the primary component of DNA, which causes the ionization of DNA atoms to break molecular bonds, DNA damage can occur. Of the cell cytoplasm. Ionizing radiation interacts with water molecules, forming peroxide and free radicals that affect DNA. This has the important implication—and the experiment supports it—that the more actively a cell divides, the more radiation damage it experiences. Bone marrow cells typically have similar activity to cancer cells, which are actively dividing and expanding quickly. As a result, if cancer cells are more active than the tissues around them, radiation's harmful effects will harm them more severely. This determines the effectiveness of radiation therapy with the same exposure of tumor cells and large volumes of healthy tissue, for example, with prophylactic irradiation of regional lymph nodes. However, due to the "focusing" of the ionizing radiation dose (by overlapping multiple beams on the same area), advanced medical devices for radiation therapy can substantially increase the therapeutic ratio. Pathological focus) and, accordingly, a more gentle effect on healthy tissues. To protect healthy tissues that are especially sensitive to radiation (for example, bone marrow), "compensators" are used - opaque screens that cover these tissues from the rays.

Types:

According to the type of particles, ionizing radiation can be divided into two groups - corpuscular:

1. α-particles,
2. β particles,
3. Neutron (the isotope 252 Cf or cyclotrons is used as a source),
4. Proton,
5. Carbon ions
6. And wave:
7. X-ray radiation,
8. γ radiation.

Indications:

The most common reason for prescribing radiation therapy is the presence of neoplasms of various etiologies. Although there is also an "exotic" application in cosmetology - irradiation after plastic surgery of keloid scars and epilation using soft x-rays. Radiation therapy has also been successfully used to treat plantar fasciitis (“heel spur”). Depending on the localization of the pathological focus, the types of exposure and the dose of radiation differ.

One of the three main modalities for treating malignant disease is radiation therapy (the other two major modalities are chemotherapy and surgery). Specific disease indications influence the choice to use radiation therapy. Ionizing radiation, for instance, usually destroys cancerous cells. However, some tumors may experience more harm before being removed. Additionally, the total dose that can be safely delivered will be limited by some normal tissues' tolerance to ionizing radiation. Thus, the effectiveness of radiation therapy depends on the type of tumor and where it is located. Tumors that cannot be surgically removed are most frequently treated with radiation therapy (e.g., brain tumors). When there is a high chance that the tumor will return after surgery, it might be added to the patient's treatment plan. To treat or prevent the emergence of metastatic disease, chemotherapy is frequently combined with radiation therapy (the spread of cancer to other parts of the body).

Applications:

There are three methods of exposure: contact (the radiation source contacts human tissues), remote (the source is at some distance from the patient), and radionuclide therapy (the radiopharmaceutical is injected into the patient's blood). Contact radiation therapy is sometimes referred to as brachytherapy.

Contact radiation therapy:

Contact exposure is produced by direct application of the radiation source to the tumor tissue, and is performed intraoperative or with superficially located neoplasms. In this regard, this method, although less harmful to surrounding tissues, is used much less frequently. With the interstitial (interstitial) method, sealed sources in the form of wires, needles, capsules, and assemblies of balls are introduced into the tissues containing the tumor focus. Such sources are both temporary and permanent implantation.

External beam radiation therapy:

With remote exposure, healthy tissues can lie between the focus of exposure and the radiation source. The more of them, the more difficult it is to deliver the required dose of radiation to the focus, and the more side effects of therapy. But, despite the presence of serious side effects, this method is the most common. This is due to the fact that it is the most versatile and affordable to use.

A promising method is proton therapy. The method allows precise targeting of the tumor and destruction of it at any depth of localization. Surrounding tissues receive minimal damage since almost the entire radiation dose is released into the tumor in the last millimeters of the particle path. One barrier to the large-scale use of protons in cancer treatment is the size and cost of the cyclotron or synchrocyclotron equipment required.

Radionuclide treatment:

In this technique, the radionuclide accumulates specifically in tissues that contain a tumor focus (either as an independent agent or as a component of a radiopharmaceutical). Open sources are utilized in this situation, and the solutions are directly injected into the body through the mouth, into a cavity, tumor, or vessel. Iodine in the thyroid gland, phosphorus in the bone marrow, strontium in the bones, etc. is a few examples of how some radionuclides can concentrate primarily in certain tissues.

Side Effects:

As a result of irradiation, not only the tumor itself suffers but also the surrounding tissues. The tumor itself dies under the action of ionizing radiation, and the decay products enter the bloodstream. Based on this, two groups of side effects can.

Radiation therapy's potential for long-term side effects depends on the tissues that are exposed to radiation beams, the patient's age, and the radiation dose. Permanent long-term effects are typical. When the growth plate is near the radiation therapy field, a young child's bone growth is impacted. When the thyroid gland or thyroid gland is exposed to high doses of radiation, hormone deficiencies can happen at any age. Learning difficulties, which can be serious if the child is very young at the time of treatment, can result from neurological function and cognitive impairment in children receiving radiation therapy for brain tumors.

One of the most devastating effects of radiation therapy is the development of secondary malignancies. Thyroid cancer, breast cancer, lung cancer, gastric and colorectal cancers, as well as soft tissue and bone sarcomas, are a few examples of such malignancies. A malignancy must have different histology than the patient's initial tumors occur within the radiotherapy field of treatment, and occur after a latency period deemed sufficient for induction of radiation-induced cancer in order to be considered radiotherapy-induced (generally five or more years).