How is radiation therapy used in prostate cancer treatment?
Radiation therapy is widely used in definitive (curative), adjuvant, and palliative treatment of prostate cancer. In radiation therapy (also called radiotherapy), high-energy X-rays are used to damage cancer cells and stop them from growing and dividing. Like surgery, radiation therapy is local therapy; it can affect cancer cells only in the treated area. In early stage prostate cancer, radiation can be used instead of surgery, or it may be used after surgery to destroy any cancer cells that may remain in the area. In metastatic diseases, it may be given to relieve pain or other problems.
Radiation may be directed at the body by a machine (external beam irradiation), or it may come from a small container of radioactive material placed directly into or near the tumor (radioactive seed implant, or brachytherapy). Some patients receive both kinds of radiation therapy.
For external radiation therapy for prostate cancer, the patient is treated in an outpatient department of a hospital or clinic. Treatment generally is given 5 days a week for about 6 weeks. This schedule helps protect healthy tissues by spreading out the total dose of radiation. The rays are aimed at the pelvis. At the end of treatment, an extra "boost" of radiation is often directed at a smaller area, where the tumor developed.
Studies have shown that prophylactic irradiation of clinically or pathologically uninvolved pelvic lymph nodes does not appear to improve overall survival or prostate cancer-specific survival. However, pelvic irradiation may significantly decrease the local recurrence in the pelvis in some patients.
Long-term results with radiation therapy are dependent on stage. A review of 999 patients treated with irradiation showed cause-specific survival rates to be significantly different at 10 years by T-stage: T1 (80%), T2 (65%), T3 (55%), and T4 (20%). An initial serum prostate-specific antigen (PSA) level of greater than 15 ng/mL is a predictor of probable failure with conventional radiation therapy.
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Radiation for Prostate Cancer - Web site of a private radiation treatment center provides very useful information about seed implant (brachytherapy).