Aspirin in Preventing Colorectal Cancer in Patients at Increased Risk of Colorectal Cancer

PRIMARY OBJECTIVE: I. Determine whether acetylsalicylic acid (aspirin) will alter spectral markers (i.e., spectral slope and fractal dimension) in distal colonic mucosa of patients who are at increased risk for the development or recurrence of colorectal cancer. SECONDARY OBJECTIVES: I. Assess the effect of this drug on colonic epithelial apoptosis and cell proliferation in these patients. II. Assess the effect of this drug on rectal prostaglandin levels in these patients. III. Assess the effect of this drug on platelet cyclooxygenase activity in these patients. IV. Correlate changes in spectral markers with UGT1A6 genotype in patients treated with this drug. OUTLINE: This is a multicenter, randomized, double-blind, placebo-controlled study. Patients are stratified by clinical site and adenoma/carcinoma maximal size. Patients with abnormal spectral biomarkers are randomized to 1 of 2 treatment arms. ARM I: Patients receive oral acetylsalicylic acid (aspirin) once daily. ARM II: Patients receive oral placebo once daily. In both arms, treatment continues for 3 months in the absence of unacceptable toxicity. Patients undergo flexible sigmoidoscopy and biopsies as well as blood collection at baseline (during prestudy colonoscopy) and at completion of study treatment for comparison of spectral signatures with biomarkers of both aspirin activity (including plasma cyclooxygenase activity and rectal prostaglandin levels) as well as with biomarkers associated with antineoplastic alteration (including apoptosis and cell proliferation). UGT1A6 genotyping analysis is also performed. After completion of study treatment, patients are followed at 3 months.