High-Dose-Rate Brachytherapy

Two hundred and nineteen thousand new cases of prostate cancer have been projected in the Unites States for 2007, with external beam radiotherapy (EBRT) constituting the mainstay of local therapy for an increasing proportion of newly diagnosed patients. Despite improvements in the delivery and reduction in associated toxicity of external beam radiotherapy, local persistence or recurrence of disease remains prevalent in 25-51% of patients. Local disease after EBRT is a risk factor for subsequent metastatic progression and prostate cancer-specific mortality, and is a cause of morbidity including hematuria, obstructive uropathy, and chronic pain. Given its prevalence, and the lack of satisfactory local salvage treatments, fear of prostate cancer recurrence has been shown to impose a substantial burden of suffering in patients. Stereotactic needle placement under MRI-guidance enables two critical steps in tumor-targeted brachytherapy: 1) directly guiding brachytherapy catheters to sites of tumor recurrence, and 2) permitting treatment planning and delivery to be based on 3D MRI images. MRI-based HDR brachytherapy will precisely identify the location of brachytherapy catheters relative to the target volumes and adjacent normal structures at risk of radiation injury, obviating the need for invasive saturation (24-100) mapping biopsies. This study will build the evidence supporting the concept of MRI-guidance and tumor-targeted HDR brachytherapy in the management of prostate cancer. This trial will strive to demonstrate improvements in technical performance under MRI-guidance, while exploring a novel paradigm of patient-specific modulation of dose intensity based on regions of tumor burden.