Adaptive Radiation Therapy (ART) Stereotactic Ablative Body Radiotherapy (SABR) for Primary Localized Prostate Cancer

This clinical trial evaluates changes in quality of life after two treatments with near margin-less adaptive radiation therapy (ART) compared to five treatments with standard stereotactic ablative body radiotherapy (SABR) in patients with prostate cancer that has not spread to other parts of the body (localized). ART is a type of radiation therapy that uses information gathered during the treatment cycle to inform, guide, and alter future radiation treatments with respect to location and dose. It may be able to deliver radiation to the site of disease over a shorter time and with smaller margins (less treatment delivered to nearby healthy tissues). SABR is a type of external radiation therapy that uses special equipment to position a patient and precisely deliver radiation to tumors in the body (except the brain). The total dose of radiation is divided into smaller doses given over several days. This type of radiation therapy helps spare normal tissue. Shorter duration near margin-less ART may be just as effective at treating patients with localized prostate cancer but have less quality of life side effects than standard SABR.