RATIONALE: Chemoprevention therapy is the use of certain drugs to try to prevent the development of cancer. The use of celecoxib has been approved for use in reducing the number of adenomatous colorectal polyps in familial adenomatous polyposis (FAP). It is not known whether there is a clinical benefit from a reduction in the number of colorectal polyps in FAP patients. The use of celecoxib may be an effective way to prevent the development of sporadic adenomatous polyps, precursors of colorectal cancer.

PURPOSE: This randomized phase III trial is studying celecoxib to see how well it works compared to a placebo in preventing the development of adenomatous colorectal polyps in patients who have had at least one polyp removed.

OBJECTIVES: I. Determine the safety and efficacy of celecoxib in reducing the occurrence of new sporadic adenomatous polyps (SAP) in the colon and rectum in patients who have undergone polypectomy for previous SAP.

OUTLINE: This is a randomized, double blind, placebo controlled study. Patients are entered on one of two treatment arms: Arm I: Patients receive celecoxib twice a day for 3 years. Arm II: Patients receive placebo twice a day for 3 years. Patients are evaluated for adenomatous colorectal polyps at 1 and 3 years.

PROJECTED ACCRUAL: Over 1000 patients will be accrued for this study.

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