DISEASE CHARACTERISTICS:

• Healthy persons at increased risk for colorectal neoplasia due to 1 of the following reasons:

  • Personal history of colorectal adenomatous polyps
  • Family history of colorectal adenoma or adenocarcinoma
• No history of multiple family members with colorectal neoplasia that is suggestive of dominant hereditary neoplasia

PATIENT CHARACTERISTICS:

Age

• 40 to 72

Performance status

• Ambulatory

Life expectancy

• At least 6 months

Hematopoietic

• No excessive bleeding or coagulation disorder

Hepatic

• ALT or AST ≤ 2 times upper limit of normal
• No unexplained elevated alkaline phosphatase

Renal

• Creatinine ≤ 2.0 mg/dL

Cardiovascular

• Homocysteine concentration ≤ 17um/L
• No sustained blood pressure > 150/95 mm Hg for 3 consecutive readings

Other

• Vitamin B_12 ≥ 250 pg/mL
• Folate level ≤ 20 mg/dL
• HIV negative
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 4 weeks after study participation
• No intestinal malabsorption or inflammatory bowel disease
• No prior malignancy except nonmelanoma skin cancer
• No calcium metabolism abnormalities or predisposing conditions, such as hyperparathyroidism
• No untreated hyperthyroidism
• No untreated insulin-requiring diabetes mellitus
• No daily alcohol intake > 2 ½ shot glasses of whiskey or three 8 ounce glasses of beer or wine
• No other serious illness that might limit life expectancy to < 6 months

PRIOR CONCURRENT THERAPY:

Biologic therapy

• None

Chemotherapy

• None

Endocrine therapy

• No concurrent hormone replacement therapy, including oral, transplanted, or injected contraceptives
• Concurrent thyroid hormone replacement is allowed as long as the patient is euthyroid for 3 months

Radiotherapy

• None

Surgery

• No prior gastrointestinal surgery, including gastrectomy or small or large bowel resections

  • Prior appendectomy or surgery of the esophagus allowed

Other

• More than 3 months since regular ingestion of ≥ 650 mg per day of aspirin (≥ 2 tablets of 325 mg regular strength OR > 1 tablet of 500 mg extra strength aspirin)
• More than 3 months since regular daily ingestion of nonsteroidal anti-inflammatory drugs
• At least 1 month since vitamin, mineral, or herbal supplementation
• No other concurrent vitamin, mineral, or herbal supplementation
• No concurrent anticoagulants
• No concurrent sterol-binding resins (i.e., cholestyramine)
• No other concurrent investigational drugs or medications that might alter rectal mucosal proliferation, folate metabolism, or renal/hepatic impairment
• No concurrent weight control medications
• No concurrent supplemental folate preparations containing > 400 mcg of folic acid per day

• No concurrent lipid-lowering medications

  • The following concurrent statin drugs are allowed provided patient has been taking a stable dose for ≥ 1 month:

    • Atorvastatin 10 or 20 mg/day
    • Fluvastatin 20 or 40 mg/day
    • Lovastatin 10 or 20 mg/day
    • Pravastatin 10 or 20 mg/day
    • Simivastatin 5 or 10 mg/day