Radiotherapy, also called radiation therapy, is the treatment of cancer and other diseases with ionizing radiation. This radiation deposits energy that injures or destroys cells in the area being treated by damaging their genetic material, making it impossible for these cells to continue to grow. Although radiation damages both cancer cells and normal cells, bu they are able to repair themselves and function properly. Radiotherapy may be used to treat localized solid tumors, such as cancers of the skin, tongue, larynx, brain or breast. It can also be used to treat leukemia and lymphoma (cancers of the blood-forming cells and lymphatic system). Radiation therapy may be used alone or in combination with chemotherapy or surgery.
In order to spare surrounding tissue the beam of radiation may also be rotated around the body, sparing the health tissue, while giving the maximum dose to the tumour. However, in order to achieve this level of accuracy, many X-rays films and Computed Tomography (CT) scans are taken to clearly identify where the tumour is. Once the precise location of the tumour is known, this information is then used to plan how the radiation can be delivered administered.
One type of radiation therapy commonly used involves photons, "packets" of energy. X-rays were the first form of photon radiation to be used to treat cancer. Depending on the amount of energy they possess, the rays can be used to destroy cancer cells on the surface or deeper in the body. The higher the energy of the x-ray beam, the deeper the x-rays can go into the target tissue.
Gamma rays are another form of photons used in radiotherapy. Gamma rays are produced spontaneously as certain elements, such as radium or uranium, release radiation as they decompose, or decay. Each element decays at a specific rate and gives off energy in the form of gamma rays and other particles. X-rays and gamma rays have the same effect on cancer cells.
4.1 External radiotherapy
External radiotherapy is given by focusing the radiation directly onto the tumour, using a radiotherapy machine. The process is painless and the principle is much like shining a light source or torch. By contrast, internal radiotherapy (also known as brachatherapy), is given either by implanting radioactive pellets or wires within or close to a tumour. Additionally, internal radiotherapy may be administered by giving a radioactive liquid by mouth or injection.
In external radiotherapy, a machine directs radiation onto the cancer and surrounding tissue. Different machines may be used: some are better for treating cancers near the skin, others are better for cancers deeper in the body depending on the amount of rays emitted.
4.2 Internal radiotherapy
Another technique for delivering radiation to cancer cells is to place radioactive implants directly in a tumor or body cavity. This is called internal radiotherapy. In this treatment, the radiation dose is concentrated in a small area, and the patient stays in the hospital for a few days. Internal radiotherapy is frequently used for cancers of the tongue, mouth, neck, etc.
Internal radiotherapy, is given either by implanting radioactive pellets or wires within or close to a tumour. Additionally, internal radiotherapy may be administered by giving a radioactive liquid by mouth or injection.
5. Side effects
Like all forms of cancer treatment, radiation therapy can have side effects. Possible side effects of treatment with radiation include temporary or permanent loss of hair in the area being treated, skin irritation, temporary change in skin color in the treated area, and tiredness. Other side effects are largely dependent on the area of the body that is treated.
Most people feel tired while they are having radiotherapy, particularly if they are having treatment over several weeks (even if they are not anaemic). The cause is not understood, but they should balance rest and exercise.
Radiotherapy sometimes affects the cells in the bone marrow which produce your blood cells. This is more likely if you are having a large area treated or if treatment is to the bones of the legs, chest, abdomen or pelvis. If this is likely in your case, you will have regular blood tests during your treatment to check the number of red blood cells in your blood.
If the level of red blood cells is low (anaemia), you may feel tired and need a blood transfusion or treatment with erythropoietin to boost your red blood cell count.
