Radiation oncology (radiotherapy) is a medical procedure of treating cancers. In the procedure, tumorous cells are exposed to ionizing radiation resulting in death of the cells and subsequent tumor shrinkage. The most responsive tumors to this mode of treatment are those that are localized and have not metastasized. Generally, this therapy is used for adjuvant, curative and palliative treatments.
The procedure acts by targeting the DNA of the exposed tissue resulting in cell death. The beams of energy are aimed at several different angles so that they intersect within the tumor. This ensures that maximum absorption of the dose occurs with minimal damage to the normal tissues. This is especially important in regions where the cells are extremely susceptible to damage such as the gut and the reproductive system (the ovaries and testes).
In attempt to get better outcomes after treatment, combination of this technique with the others that are currently available is common. It is frequently given alongside surgery. This may be done either before, after, or on both occasions. In this case, it helps in shrinking the tumor as well as minimizing the chance of recurrence. It may also be combined with hormonal therapy, immunotherapy and chemotherapy.
Several forms of the technique exist. One of them is known as total body irradiation (or TBI). It involves exposure of the whole body usually before bone marrow transplantation. One of the commonest forms used in current practice is known as external beam radiation therapy (EBRT). In this type, the source is outside the body and a beam is directed to a specific target. Systemic radiotherapy is another form. Radioactive substances, iodine for example, are injected into the body and enter the circulation system. The kill all the tumor cells that they come into contact with.
In brachytherapy, a radioactive isotope is placed within the intended area or close to it. As it decays naturally it irradiates the cancerous cells. This is done to minimize the exposure of the normal tissues. The tumors greatly responsive to this mode of therapy include those of the breast and prostate.
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