RATIONALE: Selenium may prevent or slow the growth of prostate cancer.

PURPOSE: This randomized phase II trial is studying how well selenium works in treating patients with prostate cancer.

OBJECTIVES:

• To investigate the ability of selenium to prevent progression in patients with adenocarcinoma of the prostate.
• To investigate the ability of selenium to effectively modulate biomarkers of prostate cancer.
• To determine if selenium modifies the progression of prostate cancer based on an analysis of initial biopsy, subsequent blood biomarkers, and urological symptoms.
• To further establish the safety of chronic supplementation with selenium in these patients.

OUTLINE: Patients are stratified according to Gleason score (low vs moderate). Patients are randomized to 1 of 3 treatment arms.

• Arm I: Patients receive oral placebo once daily for 48 months in the absence of disease progression or unacceptable toxicity.
• Arm II: Patients receive low-dose oral selenium once daily for 48 months in the absence of disease progression or unacceptable toxicity.
• Arm III: Patients receive high-dose oral selenium once daily for 48 months in the absence of disease progression or unacceptable toxicity.

Blood and tissue samples are collected periodically for biomarker laboratory studies. Blood samples are analyzed for levels of prostate-specific antigen, chromogranin A, alkaline phosphatase, alpha tocopherol, lycopene, and other vitamins; levels of selenium by atomic absorption spectrometry; and oxidative damage to DNA. Tissue samples are analyzed for levels of Bcl-2, p53, Ki-67, thioredoxin reductase, thioredoxin, and glutathione peroxidase by immunohistochemistry and for apoptotic index by TUNEL assay.

Patients complete urological symptom questionnaires and other questionnaires periodically.

DISEASE CHARACTERISTICS:

• Biopsy-proven adenocarcinoma of the prostate within the past 48 months
• Prostate-specific antigen < 50 ng/mL
• Gleason score < 8
• Currently undergoing "watchful waiting" for prostate cancer
• No metastatic disease

PATIENT CHARACTERISTICS:

• Life expectancy ≥ 3 years
• AST and ALT ≤ 1.5 times upper limit of normal (ULN)
• Alkaline phosphatase ≤ 1.5 times ULN
• Bilirubin ≤ 1.5 times ULN
• Creatinine ≤ 1.5 times ULN
• No other malignancy within the past 5 years, except nonmelanoma skin cancer

PRIOR CONCURRENT THERAPY:

• No prior hormone therapy, radiotherapy, chemotherapy, or surgery for prostate cancer
• At least 90 days since prior and no concurrent selenium (as a dietary supplement or as part of a multivitamin) exceeding 50 mcg/day