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