Two-fraction Versus Five-fraction Stereotactic Radiotherapy for Localized Prostate Cancer

The goal of this clinical trial is to compare two dose schedules of stereotactic radiation therapy in patients with localized prostate cancer. Historically, external beam radiation to treat localized prostate cancer was given in small treatments over a period of multiple weeks. Recent studies have shown that with newer technologies and better understanding of how prostate cancer responds to radiation, the same effective dose can be given in as few as 5 treatments. This study is comparing this newer standard course of 5 treatments with an even shorter course of just 2 treatments. The dose for the 2 treatments is based on a form of internal radiation called brachytherapy, but in this study, that dose will be given using external radiation, without the need for invasive procedures. In order to make sure that the radiation therapy is given in a way that minimizes the risk of side effects to the surrounding organs, including the rectum and bladder, prior to radiation a hydrogel material will be inserted behind the prostate in order to distance the rectum further from the prostate gland, and small gold markers will be inserted into the prostate to decrease any possible movement during treatment. The main questions are whether 2-treatment radiation is tolerated as well and is as effective at treating prostate cancer, compared to the standard 5-treatment course of radiation.