Radiation therapy can be used in multiple ways in men with metastatic prostate cancer. The most common reason to receive radiation therapy is for palliation of pain from prostate cancer spreading to bone. Radiation therapy is very effective at reducing cancer related pain and ~70-80% of patients will experience some degree of pain relief after palliative radiation therapy. Usually the radiation therapy is delivered in either 1, 5, or 10 treatments. There are usually very few side effects, as the goal of the treatment is to make you feel better and not cause more problems, so a low/moderate dose of radiation therapy is used. Other indications for radiation therapy are if you have progressive disease within the prostate causing urinary obstruction or bleeding. Radiation therapy is usually given over 1-4 weeks in these settings, and is highly dependent on if you had previous radiation therapy to the prostate. Less common indications include palliation of spine cord compression.
More recently, radiation therapy, especially SBRT (high dose, ultra-precise radiation therapy, usually in 1-5 treatments) is increasingly being used to treat men with oligometastatic disease (men who have only 1 to 5 metastatic lesions). This is an active area of research. Additionally, some researchers are investigating treating the prostate in men who present with metastatic disease at initial diagnosis.
Given the many uses of radiation therapy in advanced prostate cancer, talk to your medical oncologist and have a consultation with a radiation oncologist to see if radiation therapy is indicated.