P-314 Supine VMAT versus prone 3D-EBRT in preoperative rectal cancer: Dosimetric comparison and pathological response with each radiotherapy technique

Abstract

The use of belly-board as an immobilization system with a full bladder protocol to receive radiotherapy for rectal cancer has been a standard of care for many years. Doing this, we reduce doses to organs at risk, but the position is difficult to maintain and hardly reproducible. With advanced techniques of radiotherapy, we can achieve this protection regardless of the position of treatment. Therefore, making a dosimetric comparison between 3D-EBRT (external beam radiotherapy) in prone versus VMAT (volumetric arc radiotherapy) in supine position and pathological response achieved with these two radiotherapy techniques were the aims of this study.