Stereotactic Body Radiation Therapy With Boost Using Urethral-Sparing Intensity-Modulated Radiation Therapy Planning in Treating Patients With Prostate Cancer

PRIMARY OBJECTIVES: I. To evaluate the incidence of genitourinary (GU) and gastrointestinal (GI) acute and late toxicity for patients treated with prostate stereotactic body radiotherapy (SBRT) with simultaneous integrative boost, urethral ring sparing, and enhanced prostate localization (magnetic resonance imaging \[MRI\\-computed tomography \[CT\] fusion). II. To also evaluate the incidence of GU and GI acute and late toxicity for patients treated with prostate stereotactic body radiotherapy (SBRT) with a more conventional and uniformly delivered dose of 7.25 Gy/fraction to the prostate. III. Disease-free survival: disease-free failure events include local progression, distant progression, biochemical failure as defined by the Radiation Therapy Oncology Group (RTOG) Phoenix definition, and death from any cause. SECONDARY OBJECTIVES: I. Evaluate patient quality of life (QOL) using the Expanded Prostate Cancer Index Composite 26 (EPIC-26) for evaluation of the QOL for up to 3 years after the completion of SBRT. OUTLINE: Participants are assigned to 1 of 2 treatment arms. Participants unable to undergo MRI, whose MRI proves technically inadequate for delineating needed anatomic structures, or who decline to enroll on Arm A are assigned to Arm B. ARM A: (n = 120) Participants undergo 5 fractions of moderate dose SBRT with simultaneous integrated boost (SIB) every other day for 10 days following urethral-sparing IMRT planning. ARM B: (n = 40) Participants undergo 5 fractions of uniform dose SBRT every other day for 10 days following undergo urethral-sparing IMRT planning. After completion of study treatment, patients are followed up at 4-8 weeks, at 4, 8, and 12 months, every 4 months for 1 year, every 6 months for 3 years, and then every 12 months thereafter. Per protocol amendment in December 2023, the follow up time period for data collection will change to 3 years after the last participant completed treatment.