This study will evaluate the daily use of a unique daily organ tracking system on target localization in patients treated with radiation therapy after radical prostatectomy for prostate cancer.

Improved coverage of the target volume with radiotherapy could result in improved cancer control rates and decreased coverage of surrounding structures potentially decreasing treatment toxicity.

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.

Inclusion Criteria:

• Histologically confirmed adenocarcinoma of the prostate initially managed with prostatectomy with a detectable PSA, positive surgical margins, or extra-prostatic extension.
• Ability to comply with study schedule
• Age 40 or older
• Zubrod PS 0 or 1 (appendix 1)
• Signed informed consent

Exclusion Criteria:

• Node positive or metastatic prostate cancer
• History of prior pelvic radiotherapy
• History of abdominoperineal resection
• History of inflammatory bowel disease or connective tissue disease
• History of bleeding disorder or any active anticoagulant or anti-platelet medication which cannot be discontinued safely for transponder placement.
• PT or INR outside normal range for institution
• Active implanted devices such as cardiac pacemakers and automatic defibrillators.
• Prosthetic implants in the pelvic region that contain metal or conductive materials (eg., an artificial hip).
• Patients with maximum anterior-posterior separation through the torso minus the height of the center of the prostate greater than 17 cm (technical reason for Calypso System, see appendix 5).
• History of HIV infection

This study will include high risk patients referred for adjuvant or salvage radiation therapy after radical prostatectomy based upon the presence of unfavorable characteristics after prostatectomy, which include positive surgical margins, extracapsular extension of disease, or immediately detectable PSA.