RATIONALE: Specialized radiation therapy that delivers a high dose of radiation directly to the tumor may kill more tumor cells and cause less damage to normal tissue.

PURPOSE: This phase I trial is studying the best dose of intensity-modulated radiation therapy in treating patients with prostate cancer.

OBJECTIVES:

• To test the feasibility of delivering hypofractionated intensity-modulated radiotherapy to the prostate and pelvic nodes of patients with prostate cancer.
• To determine the optimal dose level of this treatment regimen to be used in future studies.

OUTLINE: Patients are stratified according to small bowel total volume (low small bowel volume < 450 cc vs high small bowel volume ≥ 450 cc).

Patients undergo hypofractionated intensity-modulated radiotherapy to the prostate and pelvis for 4 weeks in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up every 6 months for 5 years and then annually thereafter.

DISEASE CHARACTERISTICS:

• Diagnosis of prostate cancer meeting 1 of the following criteria:

  • Stage T3b/T4 disease or radiological or pathological pelvic nodal metastases
  • Localized disease (stage pT2-T4) with > 30% estimated risk of pelvic nodal metastases
  • High-risk (Gleason score ≥ 8 or ≥ 2 risk factors) or very high-risk disease according to the National Collaborative Cancer Network (NCCN)
  • Has undergone prostatectomy AND has stage T2-T3a, N0 disease with extensive high-risk disease (Gleason score ≥ 8) or seminal vesicle or lymph node involvement

• Candidate for radical radiotherapy

PATIENT CHARACTERISTICS:

• No inflammatory bowel disease or other small bowel disease

PRIOR CONCURRENT THERAPY:

• No prior pelvic radiotherapy or surgery (excluding prostatectomy)