CASPIR trial: Using prostatic calculi as an alternative to fiducial markers for IGRT in for localized prostate cancer.

60Background: Image guided Radiotherapy (IGRT) for prostate cancer (PCA) frequently employs surgically implanted fiducial markers (FMs). However, it is estimated that up to 35% of prostate radiotherapy patients have prostatic calculi (PC) visible on treatment cone beam CTs (CBCT). The purpose of this clinical trial is to directly compare FMs with PCs as an aid to prostate IGRT. Methods: We report data from a single institution prospective clinical trial investigating the feasibility of using prostate calcifications as natural FMs for IGRT. Patients planned for standard prostate radical EBRT +/- brachytherapy were eligible. Prior to CT planning, 3 gold fiducial markers are inserted into the prostate by the trans-perineal route under TRUS guidance. PCs visible within the PTV were contoured. Participants were aligned to FMs for EBRT using daily CBCT image guidance on a Varian TrueBeam linac. Off-line, a single experienced user analyses CBCTs using Image Registration in Eclipse (version 13.6). Random and syst...