Stereotactic Body Radiation Therapy or Intensity-Modulated Radiation Therapy in Treating Patients With Stage IIA-B Prostate Cancer

PRIMARY OBJECTIVES: I. To determine whether stereotactic body radiation therapy (SBRT) can be shown to be superior to hypofractionated intensity-modulated radiation therapy (IMRT) in terms of genitourinary (GU) and gastrointestinal (GI) toxicity by having fewer patients that experience a minimal important decline (MID) in urinary irritation/obstructive and bowel Health Related Quality of Life (HRQOL) as measured by Expanded Prostate Cancer Index Composite (EPIC)-26 at 24 months post completion of therapy. II. To determine if SBRT (5 fractions of 7.25 Gy) is superior to hypofractionated IMRT (28 fractions of 2.5 Gy or 20 fractions of 3 Gy) as measured by disease free survival (DFS). SECONDARY OBJECTIVES: I. To determine whether SBRT can be shown to be superior to hypofractionated IMRT at 12 and 24 months post completion of therapy in terms of HRQOL by having fewer patients that experience a minimal important decline (MID) bowel (12 months only) sexual, hormonal, urinary irritation/obstructive (12 months only) and in urinary incontinence HRQOL as measured by EPIC-26. II. To determine if SBRT (5 fractions of 7.25 Gy) is superior to hypofractionated IMRT (28 fractions of 2.5 Gy or 20 fractions of 3 Gy) as measured by biochemical failure, overall survival, local failure, prostate cancer specific survival, and distant metastases. III. To determine the correspondence between the diagnostic magnetic resonance imaging (MRI) and biopsy. IV. To determine if prostate imaging-reporting and data system (PIRADS)version (v)2.1 = 4/5 disease is prognostic for biochemical failure. EXPLORATORY OBJECTIVES: I. To determine whether a potentially more expensive therapy, SBRT, would be cost-effective than standard hypofractionated IMRT as measured by the European Quality of Life Five Dimension Five Level Scale Questionnaire (EQ-5D-5L). II. To determine if disease characteristics captured on baseline and follow-up MRI can be used to predict which patients will respond to SBRT versus hypofractionated IMRT. III. To validate autosegmentation tools for the prostate and tumors. IV. Collect specimens for future translational research analyses. OUTLINE: Patients are randomized into 1 of 2 arms. ARM I: Patients undergo IMRT once daily for 5 fractions per week for 20 or 28 fractions over less than 32 business days. ARM II: Patients undergo SBRT at least every other day for 2-3 fractions per week over less than 17 business days. After completion of study treatment, patients are followed up every 3 months for 2 years, every 6 months for 3 years, and then annually thereafter.