Curative Radiation Therapy
Radiation therapy plays a very important role in cancer treatment, using radiation to kill cancer cells and while causing minimal damage to normal cells and tissue. More than half of all cancer patients receive radiation therapy.
The decision to treat a tumor with radiation is based on the location of the primary tumor and whether the tumor cells are radiosensitive. Although radiation therapy and surgery have similar cure rates for some types of cancer, radiation therapy is preferred to surgery if the patient has a preexisting condition that makes surgery impossible or if surgery would require removing part or all of an organ. For example, radiation therapy may be chosen to treat cancer of the larynx in order to preserve the voice.
Radiosensitive tumors respond by promptly showing regression after moderate doses of radiation. Two examples of highly radiosensitive cancers are leukemia (cancer of the blood cells) and lymphoma (cancer of the lymphatic system).
Radiation therapy is most effective when a tumor is contained, easily accessible, and located away from major organs of the body. Testicular cancer, for example, is one of the best candidates for radiation therapy. During the process of radiation therapy for testicular cancer, the rest of the body can be easily protected from the radiation. Radiation can be directed from all angles to increase the effectiveness of the treatment.
Radiocurability means that the normal tissue-tumor relationship is such that curative doses of radiation can be used without excessively damaging the normal tissue. Radiocurative tumors include carcinoma of the cervix, larynx, breast, and prostate. Radiation may be the only therapy necessary for radiocurative tumors.
Generally, radiation is directed to the tumor and the immediate surrounding area. This destroys the main tumor and any nearby tumor spread. Higher total doses of radiation are needed to destroy the main tumor; lower doses are given to destroy the spread of the tumor. Because radiation affects both normal and cancerous cells, radiation fields are very carefully planned (by radiation therapists and physicists) to exclude uninvolved vital organs and tissues. Patients are treated with multiple small doses of radiation with time in between treatments so their healthy cells can repair much of the radiation damage.
The doctor in charge of the patient's radiation therapy is called a radiation oncologist, who develops and prescribes each cancer patient's radiation treatment plan and makes sure that every treatment is accurately given. The radiation oncologist works closely with other physicians and all members of the radiation oncology team, who are trained in the safe use of radiation, to make sure the cancer patient gets the best possible treatment.
Palliative Radiation Therapy
In addition to its curative purposes, radiation therapy may also be given to relieve pain in cancer patients. For example, radiation therapy can often relieve the pain caused by secondary bone cancer despite the uncertainty about how it works. For palliative purposes, lower doses are given than for curative treatment, usually over a shorter period of time.
In order to achieve the most effective cancer curative results, radiation treatment is frequently used as adjuvant therapy to other treatments. Radiation treatment may be administered before or after surgical treatment. Sometimes, surgery may effectively remove the gross tumor, but there may be a limit to the amount of adjacent tissue that can be removed without impairing function. Post-surgery radiation treatment can be administered to destroy microscopic residual cancer cells left after surgery. Sometimes, pre-surgery radiation treatment is administered to shrink the tumor so that it can be surgically removed more easily or make the operation less radical, thereby preserving more normal tissue. Based on studies, better cancer treatment outcomes result after the combination of radiation therapy and/or chemotherapy after surgery.
To ensure the success of radiation treatment, the radiation oncologist tailors each patient's treatment to make sure it is safe and effective. A careful treatment plan is often made, and then practiced using a simulator before any actual treatment begins.