This prospective study evaluates the clinical utility of a novel real-time localization system of the prostate bed during adjuvant or salvage radiotherapy after radical prostatectomy. This study will also determine positioning errors using daily cone-beam computed tomography in patients set up with the Calypso 4D Localization System. Subjects will have Beacon® Transponders implanted into the prostate bed. The Calypso 4D Localization System will localize the position of the prostate bed. Cone beam CT will be used daily to measure inter-transponder distance. The Calypso system will also track the prostate bed position in real time during the entire radiation treatment. The treatments will be adjusted as required to ensure accurate treatment of the clinical target volume. The time of, the number, and extent of adjustments will be recorded for analysis.
Daily cone-beam computed tomography images will also be retrospectively analyzed to assess for adequate target coverage. The analysis will be performed retrospectively through manual 3-D registration of the cone-beam CT dataset with the treatment planning CT scan. This information will determine the margins necessary for the PTV using the Calypso 4D Localization System and potentially may allow a reduction in the PTV volumes on future studies.
