Evaluation of Late Toxicity Following Intensity-Modulated Radiotherapy and Two Image-Guided Strategies With Corresponding Treatment Margins.

Prostate cancer is the most frequent cancer in men. Radiotherapy is one of the reference treatments for localized prostate cancer. Prostate was initially thought to be a non-moving target, but the newest reports have raised the contrary as evidence. Image-guided radiotherapy (IGRT) is a current standard treatment for localized prostate cancer which enables to take into account interfractional prostate motion before treatment. The Calypso® System (Varian Medical Systems, Inc., Palo Alto, CA) is a recent technology using electromagnetic transponders implanted within the prostate. It is a real-time target tracking system that takes into account both inter- and intrafractional target motion. So the exact position and movement of the prostate can be determined during radiation therapy treatment. As Planned Target Volume (PTV) margins integrate set-up margins and the management of organ motion, margin reduction can reasonably be considered in case of target motion management improvement. To date, no prospective randomized clinical data is available using this technique for the treatment of low- or intermediate-risk prostate cancer patients with modern standard fractionation radiotherapy and image guidance. The aim of this study is to assess pelvic late toxicity rate after intensity-modulated radiotherapy (IMRT) when using the Calypso® System with a reduction of treatment margins. In this randomized study, patients will receive IGRT treatment using the Calypso system or a conventional IGRT treatment.