Cyclooxygenase-2 expression and recurrence of colorectal adenomas: effect of aspirin chemoprevention

Background Low-dose aspirin reduces the incidence of colorectal cancer and recurrence of adenomas. Cyclooxygenase-2 (COX-2), one of its main target enzymes, is reportedly over-expressed in colorectal adenomas.Aim To assess COX-2 expression, in relation to adenoma recurrence and the protective effect of aspirin, in a large series of colorectal adenomas, recruited from a double-blind randomised controlled trial comparing recurrences after low-dose aspirin or placebo. Methods Follow-up colonoscopies were performed after 1 and 4 years to assess adenoma recurrence. COX-2 expression was assessed by immunohistochemistry for each adenoma obtained at baseline colonoscopy, separately for epithelium, deep stroma and overall. Architecture, grade of dysplasia, K-ras mutation, p53 and cyclin D1 expression were studied. Results COX-2 expression could be assessed in 219 adenomas from 136 patients: 128 adenomas (58%) from 59 patients strongly expressed COX-2. Strong COX-2 expression predominated in adenomas larger than 10 mm (84/129 vs 44/90; p=0.02) and in adenomas showing high-grade dysplasia (22/29 vs 104/188; p=0.04). Deep stromal but not epithelial initial expression of COX-2 predicted adenoma recurrence in the whole population (30/72 patients or 42% strongly expressed deep stromal COX-2 compared with16/64 or 25% without recurrent adenoma; p=0.04). The protective effect of aspirin was mainly observed in patients in whom COX-2 initial expression was low (RR for recurrence in patients taking aspirin with low COX-2 expression: 0.59; 95% CI 0.39 to 0.90; p=0.02). There was no significant effect of aspirin at the end of the trial. Conclusion Over-expression of COX-2 was frequent and predominated in large and high-grade dysplasia adenomas. Deep stromal but not epithelial initial expression of COX-2 predicted recurrence of adenomas. Aspirin did not act preferentially on patients whose initial adenomas strongly expressed COX-2

Prevention by daily soluble aspirin of colorectal adenoma recurrence: 4-year results of the APACC randomised trial

Background Aspirin inhibits colorectal carcinogenesis. In a randomised double-blind placebo-controlled trial, daily soluble aspirin significantly reduced recurrence of colorectal adenomas at 1-year follow-up. In this study the results of daily intake of low-dose aspirin on polyp recurrence at 4-year follow-up are presented.Methods 272 patients (naive for chronic aspirin use) with colorectal adenomas were randomly assigned to treatment with lysine acetylsalicylate 160 mg/day (n=73) or 300 mg/day (n=67) or placebo (n=132) for 4 years. The primary endpoints were adenoma recurrence and adenomatous polyp burden at year 4, comparing aspirin at either dose with placebo. The same endpoints were also assessed at year 1 or 4 (last colonoscopy performed for each patient). Results At the final year 4 colonoscopy the analysis included 185 patients (55 receiving aspirin 160 mg/day, 47 aspirin 300 mg/day and 83 placebo). There was no difference in the proportion of patients with at least one recurrent adenoma between patients receiving aspirin at either dose and those treated with placebo (42/102 (41%) vs 33/83 (40%); NS) or in the adenomatous polyp burden (3.1±5.8 mm vs 3.4±6.2 mm; NS). Also, the proportion of patients with at least one advanced recurrent adenoma did not differ (10/182 (10%) in the aspirin group vs 7/83 (7%) in the placebo group; NS). Conclusion Daily low-dose aspirin decreased adenoma recurrence significantly at 1 year but not at year 4. This discrepancy might be explained by a differential effect of aspirin according to the natural history of the polyp. Trial Registration Number NCT 00224679