In this method, x-ray treatments are given with a machine that sends high-energy x-rays through the patient’s body, aimed at the prostate gland and sometimes the pelvic lymph nodes. External beam radiotherapy is a totally non-invasive treatment used as an option for men who are considered too old or too ill for a prostatectomy or who just don’t want surgery. It is difficult to determine whether external beam radiation actually eradicates all of the prostate cancer because many patients in whom progression of the tumor is slowed or halted have persistent tumor on repeat rebiopsy. The best results are obtained when tumors are less than 2 centimeters in size at the time of therapy.