DISEASE CHARACTERISTICS: At least one prior colorectal adenomatous polyp removed by polypectomy within the past 5 months and meeting any of the following criteria: One adenomatous polyp at least 6 cm in size Two or more adenomatous polyps of any size One adenomatous polyp and a documented history of adenomatous polyps No history of familial polyposis or hereditary nonpolyposis colorectal cancer No history of inflammatory bowel disease

PATIENT CHARACTERISTICS: Age: 30 and over Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: No chronic or acute hepatic disorder Renal: No chronic or acute renal disorder Other: No prior participation in this study No significant bleeding disorder or other condition that would preclude study therapy No history of hypersensitivity to COX-2 inhibitors, NSAIDS, salicylates, or sulfonamides No prior invasive cancer within the past 5 years other than nonmelanomatous skin cancer Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: At least 2 months since prior oral corticosteroids received 3 or more times per week At least 6 months since prior oral or intravenous corticosteroids received for more than 2 weeks duration No anticipated oral or intravenous corticosteroid use of more than 2 weeks duration over the next 6 months At least 6 months since prior inhaled corticosteroids received for more than 4 weeks duration No anticipated inhaled corticosteroid use of more than 4 weeks duration over the next 6 months Use of mometasone (Nasonex) is not restricted (all other nasal steroids are prohibited) Radiotherapy: Not specified Surgery: No prior large bowel resection other than appendectomy Other: At least 1 month since any prior treatment for gastrointestinal ulcer At least 2 months since prior nonsteroidal anti-inflammatory drugs (NSAIDS), other than aspirin, received 3 or more times per week No concurrent chronic NSAIDS, defined as a frequency of 1-week (7 consecutive days) for more than 3 weeks per year At least 1 month since prior investigational medications No other concurrent investigational drugs No concurrent fluconazole or lithium