RATIONALE: Chemoprevention therapy is the use of certain drugs to try to prevent the development or recurrence of cancer. The use of aspirin may be an effective way to prevent the recurrence of polyps in colorectal cancer.

PURPOSE: Randomized phase III trial to study the effectiveness of aspirin in treating patients who have stage I, stage II, or stage III colorectal cancer that has been surgically removed.

OBJECTIVES: I. Determine whether aspirin administered at a dose of 325 mg/day will decrease the number and size of new adenomas in patients with Dukes' A/B1/B2/C colorectal cancer who have undergone curative surgical resection. II. Assess whether this dose of aspirin will increase disease-free survival in these patients.

OUTLINE: Randomized, double-blind study. Arm I: Chemoprevention. Enteric-coated Aspirin, ASA, NSC-27223. Arm II: Control. Placebo, PLCB.

DISEASE CHARACTERISTICS: Histologically documented colorectal cancer that has been curatively resected, including: Dukes' A/B1 (T1-2, N0, M0) Dukes' B2/C (T3, N0, M0 and any T, N1, M0) disease-free more than 5 years post-resection Colonoscopy to the cecum (or small bowel anastomosis) with removal of all polyps required within 4 months of entry Preparation must be adequate to visualize mucosa and discern the presence of no further polyps No familial polyposis (more than 100 polyps at time of resection) No history of inflammatory bowel disease including ulcerative colitis or Crohn's disease

PATIENT CHARACTERISTICS: Age: 30 to under 75 Performance status: Physician's assessment of good general health required Life expectancy: At least 5 years Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Cardiovascular: No NYHA class III/IV status No history of angina No history of MI No history of stroke or TIAs No peripheral vascular disease No bleeding diathesis including hemorrhagic stroke No prophylactic aspirin for cardiovascular disease Other: No documented peptic ulcer disease within past 15 years No aspirin sensitivity including: Aspirin-induced asthma Bronchial hyper-reactivity Urticaria Angioedema No requirement for sodium warfarin or other anticoagulant No frequent (greater than 36 times/year) NSAID use within the past 5 years No recurrent arthritis or other musculoskeletal problems No narcotic or alcohol dependency (unless there has been at least a 6-month period of abstinence) No prior or concurrent malignancy within 5 years (including metastases) except nonmelanomatous skin cancer No pregnant or nursing women Effective contraception required of fertile women

PRIOR CONCURRENT THERAPY: No concurrent enrollment in a colon cancer treatment trial or other chemoprevention trial Biologic therapy: At least 6 months since immunosuppressive therapy (i.e., azathioprine, methotrexate, cyclosporine) Chemotherapy: Prior chemotherapy allowed for patients with Dukes' B2/C colorectal cancer No concurrent chemotherapy Endocrine therapy: Prior non-immunosuppressive steroid treatment allowed Radiotherapy: Prior radiotherapy allowed for patients with Dukes' B2/C colorectal cancer No concurrent radiotherapy Surgery: Curative resection required