Rofecoxib After Surgery in Treating Patients With Stage II or Stage III Colorectal Cancer

DISEASE CHARACTERISTICS: Histologically confirmed colorectal carcinoma Stage II (T3-4, N0, M0) or stage III (any T, N1-2, M0) disease Completely resected primary tumor without gross or microscopic evidence of residual disease Must have received potentially curative therapy within the past 12 weeks, including any of the following: Surgery alone Surgery plus radiotherapy and/or chemotherapy PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-1 Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) AST/ALT no greater than 1.5 times ULN Renal: Creatinine clearance greater than 30 mL/min Cardiovascular: No severe congestive heart failure Other: Not pregnant or nursing Fertile patients must use effective contraception No active peptic ulcer or gastrointestinal bleeding within the past year No inflammatory bowel disease No known sensitivity to rofecoxib No prior adverse reaction to non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., asthma, acute rhinitis, nasal polyps, angioneurotic edema, or urticaria) No other malignancy within the past 10 years except adequately treated carcinoma in situ of the cervix or basal cell or squamous cell skin cancer PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: See Disease Characteristics Endocrine therapy: Not specified Radiotherapy: See Disease Characteristics Surgery: See Disease Characteristics Other: No concurrent long-term NSAIDs except low-dose aspirin (no more than 80 mg/day) for cardio-prophylaxis