Risk of colorectal cancer following colonoscopic polypectomy

Aims and Background: To follow a cohort of patients who had undergone polyp ectomies in order to assess the overall risk of subsequent colorectal cance r in relation with various adenomas characteristics. Methods: A total of 1,063 patients with adenomatous polyps of the large int estine were treated between 1979 and 1996 at the National Cancer Institute of Milan, during a screening program for colorectal carcinoma. Data on pati ents who had undergone colonoscopies were collected prospectively, The rela tion between colorectal cancer and adenomas characteristics was assessed by computing the hazard ratio (HR) values and corresponding confidence interv als (95% CI), according to Cox. Results: Of the 1,063 patients who met the eligibility requirements, 672 ha d single adenomas (63.2%) and 391 had multiple adenomas (36.8%). Histologic al examination revealed 743 cases of tubular adenoma, 196 cases of tubulo-v illous adenoma, and 96 cases of villous adenoma. High-grade dysplasia was f ound in 3.1% of the cases. During the 8,906 persons/year of follow-up, aden ocarcinomas of the large bowel developed in 11 patients. Several adenomas' characteristics at index polypectomy were significant predictors of colorec tal cancer occurrence. In univariate analysis the risk of colon cancer was significantly related with multiple adenomas (HR 4.2, 95% CI 1.1-6.5), high -grade dysplasia adenomas (HR 10.0, 95% CI 2.6-38.1) and with adenomas larg er than 2 cm (HR 5.0, 95% CI 1.2-20.4). A multivariate stepwise procedure c onfirmed that the presence of multiple adenomas and presence of high-grade dysplasia are the most important predictors of carcinomas. Hazard ratios fo r colorectal cancer occurrence, from multivariate Cox's model, were 5.1 (95 % CI 1.2-19.9) for multiple compared to single adenomas, and 13.0 (95% CI 3 .6-50.7) adenomas with high-grade dysplasia compared to those with low-grad e dysplasia. Conclusions: High-grade dysplasia, number and size of adenomas were confirm ed as the major cancer predictors. Based on this conclusion, a subgroup of patients, who may benefit from intensive surveillance colonoscopy, can be i dentifiable.