DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • Clinical stage T1b, T1c, or T2a disease
  • Gleason score ≤ 6
  • Maximal prostate-specific antigen (PSA) < 10 ng/mL
• Demonstrates intra-prostatic metabolite abnormalities, consistent with adenocarcinoma of the prostate (i.e., ≥ 3 voxels with magnetic resonance spectroscopy imaging [MRSI] scores 4-5) by baseline MRI and MRSI
• Has symptomatic benign prostatic hypertrophy and is currently undergoing watchful waiting OR opting to undergo permanent seed implant (i.e., brachytherapy), but requires neoadjuvant androgen suppression for prostate shrinkage
• No regional lymph node involvement
• No evidence of distant metastases

PATIENT CHARACTERISTICS:

• Zubrod performance status 0-1
• Able to swallow and retain oral medications
• No other prior or concurrent invasive cancer, other than localized basal cell or squamous cell carcinoma of the skin

• No contraindications to MRI/MRSI, including any of the following:

  • Prostate biopsy (within the past 8 weeks) and any continued post-biopsy bleeding
  • Rectal bleeding
  • Anal fissures
  • Rectal surgery (end-to-end anastomosis)
  • Inflammatory bowel disease
  • Prior radical prostatectomy
  • Hip replacement
  • Certain types of penile implants
  • Vascular clips
  • Known anaphylactic reaction to latex compounds
  • Anticoagulant drugs
  • Severe claustrophobia
  • Cardiac pacemaker
  • Metal in eye
  • Any other metallic or foreign object in the body
• No unstable serious co-morbidities including, but not limited to, myocardial infarction, coronary artery syndrome, cardiac arrhythmias, symptomatic congestive heart failure, or cerebrovascular accident
• No major medical or psychiatric illness that, in the investigator's opinion, would preclude the completion of treatment and interfere with follow up
• No known hypersensitivity to any 5α-reductase inhibitor or drug chemically related to the study drug

PRIOR CONCURRENT THERAPY:

• See Patient Characteristics
• No prior radical surgery (prostatectomy) or cryosurgery for prostate cancer
• No prior pelvic irradiation, prostate brachytherapy, or bilateral orchiectomy
• No prior or concurrent cytotoxic chemotherapy for prostate cancer
• No prior hormonal therapy, such as luteinizing hormone-releasing hormone agonists (e.g., goserelin or leuprolide acetate), antiandrogens (e.g., flutamide or bicalutamide), or estrogens (e.g., diethylstilbestrol)
• No prior or concurrent finasteride, dutasteride, other drugs with known antiandrogenic properties (e.g., spironolactone or progestational agents), or any dietary or herbal supplement (e.g., selenium, vitamin E, saw palmetto, or PC-SPES)