Radiation therapy uses high energy x-rays from a linear accelerator directed at the prostate or emitted from radioactive seeds implanted in the prostate to kill the cancer cells. When prostate cancer is confined to the prostate gland, radiation therapy is an alternative to surgery. External beam therapy also is commonly used to treat prostate cancers that already may have spread outside the gland itself where surgery is not feasible. In men with advanced disease, radiation therapy can help shrink tumors and relieve pain. External beam radiation therapy is generally given five days per week for 7 to 8 weeks total. Each daily treatment takes 30 to 45 minutes.
Conformal Radiation Therapy and Intensity Modulated Radiation Therapy (IMRT)
Using sophisticated treatment planning computers to accurately outline the prostate gland from MRI and CT images, the radiation dose is molded precisely around the prostate, minimizing radiation doses to surrounding normal tissues. IMRT is the latest in 3-D conformal treatment techniques; it allows a larger radiation dose to the tumor while minimizing side effects. Virginia Mason pioneered the use of IMRT and other cutting-edge techniques to precisely target the prostate. The prostate will move ½ inch or more from day to day and within the ½ hour time frame of daily radiation therapy. By placing 3 tiny gold beacons into the prostate, it is possible to detect the position of the gland during treatment, assuring that treatment is delivered accurately and avoiding radiation to surrounding tissues. Using IMRT and the gold beacons, prostate radiation therapy is both precise and accurate.
Hormonal Therapy and Radiation Therapy
For patients with intermediate- or high-risk prostate cancer, a combination of hormonal therapy and radiation therapy is recommended because the addition of hormones (Lupron®/Zoladex®/Casodex®) improves the effectiveness of radiation therapy. Hormonal therapy is generally initiated 2 to 6 months before the radiation therapy and sometimes continued for as long as two years.
The side effects from external beam radiation therapy are most commonly related to the radiation’s effects on organs adjacent to the prostate. Physical side effects include diarrhea, blood in the stool and rectal irritation. Other common side effects during treatment include frequent urination and burning sensation while urinating. Bladder problems can persist, with the most common problem being urinary frequency. Radiation therapy does not cause urinary incontinence. Sexual function may be affected by radiation therapy.