DISEASE CHARACTERISTICS:

• Adenocarcinoma of the prostate treated primarily with radical prostatectomy

  • Pathologically proven to be lymph node-negative by pelvic lymphadenectomy (N0) or lymph node status pathologically unknown (Nx [undissected pelvic lymph nodes because lymph node dissection is not required])
  • Any type of radical prostatectomy allowed, including retropubic, perineal, laparoscopic or robotically assisted

  • Meets 1 of the following pathologic classifications:

    • T3 N0/Nx disease
    • T2 N0/Nx disease with or without positive prostatectomy margins
  • N1 patients are ineligible, as are those with pelvic lymph node enlargement ≥ 1.5 cm in greatest dimension by CT scan or MRI of the pelvis, unless the enlarged lymph node is negative
  • Prostatectomy Gleason score of 8 or less
• A post-radical prostatectomy entry PSA of ≥ 0.1 and ≤ 1.0 ng/mL at least 6 weeks after prostatectomy and within 30 days of registration
• Serum total testosterone ≥ 40% of the lower limit of normal (patients who have had a unilateral orchiectomy are eligible as long as this requirement is met)
• No distant metastases based on history/physical examination, CT scan or MRI of the abdomen and pelvis, and bone scan
• No palpable prostatic fossa abnormality/mass suggestive of recurrence, unless shown by biopsy under ultrasound guidance not to contain cancer

PATIENT CHARACTERISTICS:

• Zubrod performance status 0-1
• Platelets ≥ 100,000/mm^3
• Hemoglobin ≥ 10.0 g/dL (the use of transfusion or other intervention to achieve this is allowed)
• AST or ALT < 2 x upper limit of normal
• No prior invasive malignancy (except nonmelanoma skin cancer) unless disease-free for a minimum of 5 years (e.g., carcinoma in situ of the oral cavity is permissible)

• No severe, active co-morbidity, including any of the following:

  • History of inflammatory bowel disease
  • History of hepatitis B or C
  • Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months
  • Transmural myocardial infarction within the past 6 months
  • Acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration
  • Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy at the time of registration
  • Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects

  • Acquired immune deficiency syndrome (AIDS) based upon current CDC definition

    • HIV testing is not required for entry
• No prior allergic reaction to the study drug(s) involved in this protocol

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No androgen deprivation therapy started prior to prostatectomy for > 6 months duration
• No androgen deprivation therapy started after prostatectomy and prior to registration
• No prior pelvic radiotherapy