Retrospective evaluation of planning margins for patients undergoing radical radiation therapy treatment for bladder cancer using volumetric modulated arc therapy and cone beam computed tomography.

Current contouring guidelines for curative radiation therapy for muscle-invasive bladder cancer (MIBC) recommend margins of 1.5-2.0 cm, applied to the clinical target volume (CTV). This study assessed whether the use of volumetric modulated arc therapy (VMAT), cone beam computed tomography (CBCT) and strict bladder preparation allowed for a reduced planning target volume (PTV) expansion, resulting in lower doses to surrounding organs at risk (OARs).