Selenium for Prevention of Adenomatous Colorectal Polyps

DISEASE CHARACTERISTICS: Histologically confirmed colorectal adenomatous polyps Meets the following criteria by colonoscopy (performed within the past 6 months): Cecum was totally visualized or reached At least 90% visualization of colon surface area Removed at least 1 adenomatous polyp of at least 3 mm in size during procedure (For the Advanced Adenoma Sub-study: Removal of at least 1 advanced colorectal adenomatous polyp during procedure. An adenoma is considered advanced if it is 10 mm or greater in size, and/or has villous histology and/or shows high grade dysplasia) Removed no more than 10 adenomatous polyps of any size by endoscopy All other neoplastic and non-neoplastic colon polyps must have been completely removed (except for diminutive [less than 3 mm] sessile rectal polyps) For the sub-study, at least 1 advanced adenomatous polyp defined as 10 mm or greater in size and/or has villous histology and/or shows high grade dysplasia No prior diagnosis of any of the following: Colorectal cancer Familial adenomatous polyposis Ulcerative colitis Crohn's disease Hereditary non-polyposis colon cancer (HNPCC), defined as: Histologically confirmed colorectal cancer in at least 3 relatives, 1 of whom is a first-degree relative of the other 2 Disease occurrence in at least 2 consecutive generations Colorectal cancer diagnosis in at least 1 family member who is less than 50 years of age Patients with a family history of colorectal cancer but who are not diagnosed with HNPCC are allowed No more than 1 prior segmental colon resection PATIENT CHARACTERISTICS: Age 40 to 80 Performance status SWOG 0-1 Life expectancy Not specified Hematopoietic Hemoglobin > 11 g/dL WBC 3,000 - 11,000/mm^3 Hepatic AST and ALT < 2 times upper limit of normal Bilirubin < 2.0 mg/dL Renal Creatinine < 1.9 mg/dL Cardiovascular No unstable* cardiac disease despite medication (e.g., diuretics or digitalis) No uncontrolled hypertension (i.e., systolic blood pressure ≥ 170 mm Hg and/or diastolic blood pressure ≥ 110 mm Hg) despite medication NOTE: *Unstable defined as unable to walk across the room without chest pain or shortness of breath Other Not pregnant or nursing Fertile patients must use effective contraception for at least 2 months before and during study treatment Resident of a clinical center metropolitan area or obtaining regular health care in a clinical metropolitan area for at least 6 months out of the year Must be able to swallow pills No unexpected weight loss of 10% or more within the past 6 months No prior rheumatoid arthritis No poorly controlled diabetes mellitus despite medication, defined as: Blood sugar level ≥ 200 mg/dL on more than half of the readings taken within the past month No invasive malignancy within the past 5 years that required medical excision, radiotherapy, or chemotherapy except basal cell or squamous cell carcinoma PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent drugs that regulate the immune system Chemotherapy No concurrent chemotherapy Endocrine therapy Not specified Radiotherapy No concurrent radiotherapy Surgery See Disease Characteristics Other Prior enrollment in another adenoma prevention study allowed Concurrent routine aspirin (≤ 81 mg/day) allowed No regular use of non-steroidal anti-inflammatory drugs (NSAIDs) No concurrent enrollment in another research study using pharmacological cancer drugs, a cyclo-oxygenase-2 inhibitor, or selenium No other concurrent selenium unless dosage is ≤ 50 µg/day