Positioning errors and prostate motion during conformal prostate radiotherapy using on-line isocentre set-up verification and implanted prostate markers.

Purpose: To evaluate treatment errors from set-up and inter-fraction prostatic motion with port films and implanted prostate fiducial markers during conformal radiotherapy for localized prostate cancer.

Methods: Errors from isocentre positioning and inter-fraction prostate motion were investigated in 13 men treated with escalated dose conformal radiotherapy for localized prostate cancer. To limit the effect of inter-fraction prostate motion, patients were planned and treated with an empty rectum and a comfortably full bladder, and were instructed regarding dietary management, fluid intake and laxative use.