In Silico Comparison of Three Different Beam Arrangements for Intensity-Modulated Proton Therapy for Postoperative Whole Pelvic Irradiation of Prostate Cancer.

Proton therapy has been shown to provide dosimetric benefits in comparison with IMRT when treating prostate cancer with whole pelvis radiation; however, the optimal proton beam arrangement has yet to be established. The aim of this study was to evaluate three different intensity-modulated proton therapy (IMPT) beam arrangements when treating the prostate bed and pelvis in the postoperative setting. Twenty-three post-prostatectomy patients were planned using three different beam arrangements: two-field (IMPTB) (opposed laterals), three-field (IMPTB) (opposed laterals inferiorly matched to a posterior-anterior beam superiorly), and four-field (IMPTB) (opposed laterals inferiorly matched to two posterior oblique beams superiorly) arrangements.