Focal Radiation Therapy for the Treatment of Low or Intermediate-Risk Prostate Cancer

PRIMARY OBJECTIVES: I. Evaluate biochemical progression free survival (bPFS) using the Phoenix definition. II. Changes in quality of life. IIa. Prostate-Quality of Life (PR-QOL). IIb. Expanded Prostate Cancer Index Composite (EPIC). SECONDARY OBJECTIVES: I. Prostate-specific antigen (PSA) response at 3, 6, 12, and 24 months. II. Clinical progression free survival. IIa. Including phoenix definition, local progression by Response Evaluation Criteria in Solid Tumors (RECIST), regional progression, distant metastasis, or death. III. Distant metastasis free survival. IV. Development of castration-resistant disease. V. Overall survival. OUTLINE: Patients are assigned to 1 of 2 arms. ARM I: Patients undergo SBRT in 5 fractions over 14 days in the absence of disease progression or unacceptable toxicity. ARM II: Patients undergo HDR brachytherapy on day 1 and a second fraction within 14 days in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 6 weeks, every 3 months for up to 24 months, every 6 months for up to 60 months, and then every 8-12 months until 120 months.