Magnetic Resonance-Guided High-Dose Brachytherapy (Short-Range Radiation Therapy) for Prostate Cancer

BACKGROUND Brachytherapy, the placement of a radioactive source close to a tumor, is rapidly becoming an important modality for patients with prostate cancer because higher and more conformal doses can be safely delivered compared with external beam radiotherapy. High dose rate (HDR) temporary implants offer several treatment and research based advantages over permanent seeds, including exceptionally complex and accurate dosimetry in reference to anatomic images. Needle placement in brachytherapy procedures requires detailed image guidance, traditionally obtained with trans-rectal ultrasound (TRUS). MRI offers a 3D dataset, arbitrary imaging planes, and unparalleled soft tissue resolution of the anatomy, making it the modality of choice for imaging the prostate gland. A real-time MR-guided prostate permanent seed implant technique that utilizes both real-time MRI and real-time dosimetry has been designed, implemented and reported. Results confirm that TRUS-guided implants may be improved upon by using MRI. To our knowledge, HDR implants have not yet been performed under MR guidance in a closed bore magnet. OBJECTIVES The primary objective is to determine the quality of prostate HDR brachytherapy implants performed under MR-guidance. Quality is defined by the percentage of the planning target volume (PTV) encompassed by a given percentage of the prescribed dose. In this study an implant will be of "acceptable" quality if 80% of the PTV is encompassed by the 100% isodose (V100 80%), in accordance with RTOG guidelines. ELIGIBILITY Pathologically confirmed prostate cancer with the following features: * Gleason score greater than 6, or greater than T2a, or * PSA greater than or equal to 10, and no evidence of bone metastases; Age greater than or equal to 18 years; ECOG performance status of 0 or 1 DESIGN The study is designed with a "run-in" pilot phase with the objective of refining the technique. The evaluation phase is a two-stage optimal design to evaluate the quality of the implant with an early look for futility. This study has the potential to enroll a maximum of 27 patients. Radiation treatment parameters will be patterned after established guidelines in the literature such as those reported by the American Brachytherapy Society and the William-Beaumont Hospital. There will be no attempted dose escalation or attempts to prescribe the dose to unconventional target volumes in this phase of the project.