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. It is not yet known which schedule of intensity-modulated radiation therapy is more effective in treating patients with prostate cancer.

PURPOSE: This randomized phase III trial is studying the side effects of three schedules of intensity-modulated radiation therapy and compares how well they work in treating patients with localized prostate cancer.

OBJECTIVES:

• Determine the safety and efficacy of conventional vs hypofractionated high-dose intensity-modulated radiotherapy in patients with localized prostate cancer.
• Determine the side effects of these regimens in these patients.
• Determine whether hypofractionated radiotherapy schedules will improve the therapeutic ratio by either improving tumor control or reducing normal tissue side effects.
• Compare acute and late treatment-related gastrointestinal and urological toxicity in these patients.
• Determine different prostate-specific antigen-related endpoints for local failure and distant metastases.
• Extend the database of patients treated to escalated doses with dose-volume histograms (DVHs) of normal tissues at risk and relate these to common toxicity endpoints.
• Develop a model to estimate normal tissue complication probability (NTCP) of rectum and bladder for hypofractionated as well as conventional dose-escalated radiotherapy schedules.

OUTLINE: This is a multicenter, randomized, pilot study. Patients are stratified according to risk of seminal vesicle involvement (low-risk vs moderate-risk or high-risk).

• Hormone therapy: Patients receive androgen-deprivation therapy comprising an injection of luteinizing hormone-releasing hormone (LHRH) agonist once monthly for 3-6 months and oral cyproterone acetate beginning the week before the first LHRH agonist injection and continuing for at least 2 weeks after each LHRH agonist injection. Within one week after the last LHRH agonist injection, patients proceed to radiotherapy.

• Radiotherapy: Patients are randomized to 1 of 3 treatment arms.

  • Arm I: Patients undergo conventional high-dose intensity-modulated radiotherapy (IMRT) in 37 fractions over 7.5 weeks.
  • Arm II: Patients undergo hypofractionated high-dose IMRT in 20 fractions over 4 weeks.
  • Arm III: Patients undergo hypofractionated high-dose IMRT in 19 fractions over 3.8 weeks.

In all arms, treatment continues in the absence of unacceptable toxicity.

Quality of life is assessed periodically during study treatment.

After completion of study treatment, patients are followed periodically for up to 15 years.

Peer Reviewed and Funded or Endorsed by Cancer Research UK

PROJECTED ACCRUAL: A total of 2,163 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate, meeting the following criteria:

  • Clinical stage T1b-T3a, N0, M0
  • Locally confined disease
  • Previously untreated disease

• Prostate-specific antigen (PSA) ≤ 30 ng/mL

• Estimated risk of seminal vesicle involvement < 30%

  • Estimated risk of seminal vesicle involvement is defined as PSA + ([Gleason score - 6] x 10) (i.e., if Gleason score ≤ 6, then PSA must be ≤ 30 ng/mL; if Gleason score = 7, then PSA must be < 20 ng/mL; if Gleason score = 8, then PSA must be < 10 ng/mL; if Gleason score = 9 or 10 patient is ineligible)

PATIENT CHARACTERISTICS:

• WHO performance status 0 or 1
• Life expectancy > 10 years (5 years for patients with poorly differentiated cancers)
• WBC > 4,000/mm^3
• Hemoglobin > 11g/dL
• Platelet count > 100,000/mm^3
• No other active malignancy within the past 5 years except basal cell carcinoma
• No hip prosthesis or fixation that would interfere with standard radiation beam configuration
• No comorbid conditions likely to impact on the advisability of radical radiotherapy (e.g., previous inflammatory bowel disease, previous colorectal surgery, significant bladder instability, or urinary incontinence)

PRIOR CONCURRENT THERAPY:

• No prior pelvic radiotherapy
• No prior radical prostatectomy
• No prior androgen-deprivation therapy
• No concurrent full anticoagulation therapy with warfarin or heparin