RATIONALE: Radiation therapy uses high-energy x-rays and other types of radiation to kill tumor cells. Giving radiation therapy in different ways may kill more tumor cells. It is not yet known which type of radiation therapy is more effective in treating prostate cancer.

PURPOSE: This randomized phase III trial is studying different types of radiation therapy to compare how well they work in treating patients with stage I, stage II, or stage III prostate cancer.

OBJECTIVES:

• Compare the efficacy of neutron and photon radiotherapy vs hypofractionated intensity modulated radiation, in terms of a lower frequency of chronic complication rate (chronic toxicity and disease-free survival), in patients with favorable to intermediate prognosis, stage I-III adenocarcinoma of the prostate.

OUTLINE: This is a randomized, multicenter study. Patients are stratified according to stage of disease (T1 vs T2 vs T3). Patients are randomized to 1 of 2 treatment arms.

• Arm I: Patients undergo neutron radiotherapy over 15-45 minutes 5 days a week for 2 weeks followed by photon radiotherapy over 15-45 minutes 5 days a week for 5 weeks.
• Arm II: Patients undergo photon radiotherapy over 15-45 minutes 5 days a week for 5 weeks followed by hypofractionated photon irradiation over 15-45 minutes 5 days a week for 2 weeks.

After completion of study treatment, patients are followed periodically for 5 years and then yearly thereafter.

PROJECTED ACCRUAL: A total of 300 patients (150 per treatment arm) will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • Stage I-III disease (T1-T3, N0, M0)

  • No clinical or radiographic evidence of metastasis

    • If prostate-specific antigen (PSA) ≥ 10.0 ng/mL and Gleason score is 7, a radioisotope bone scan must show no evidence of metastasis
    • No evidence of lymphatic or visceral metastases of the abdomen or pelvis on CT scan or MRI

• PSA ≤ 20 ng/mL

• Gleason score ≤ 7 (if stage T3 , score must be < 7)

PATIENT CHARACTERISTICS:

Performance status

• Not specified

Life expectancy

• More than 10 years

Hematopoietic

• Not specified

Hepatic

• Not specified

Renal

• Not specified

Other

• No other malignancy within the past 5 years except basal cell or squamous cell skin cancer

PRIOR CONCURRENT THERAPY:

Endocrine therapy

• Prior hormonal therapy allowed provided it was initiated no more than 2 months ago, and may include the following:

  • Luteinizing hormone-releasing hormone agonists (e.g., goserelin, leuprolide)
  • Anti-androgens (e.g., flutamide, bicalutamide)

Radiotherapy

• No prior pelvic irradiation

Surgery

• No prior radical prostatectomy