COLORECTAL POLYP COUNTS AND CANCER RISK IN FAMILIAL ADENOMATOUS POLYPOSIS

Background & Aims: In familial adenomatous polyposis, colorectal cance r prevention is by prophylactic colectomy, but dietary or chemoprevent ative strategies have been recently proposed in low-risk individuals. The aim of this study was to define predictive risk factors for colore ctal cancer in familial adenomatous polyposis. Methods: Between 1918 a nd 1993, 317 patients underwent colectomy. A multivariate analysis was performed to assess the relationship between colorectal cancer risk a nd polyp count, sex, and age at colectomy. Results: The median polyp c ount was 842 (range, 78-7500), and cancer was found in 22% of patients . Polyp count and age, but not sex, predicted cancer risk. Patients wi th >1000 polyps had 2.3 times greater risk of cancer than those with < 1000 polyps (P = 0.006). Synchronous cancers increased with polyp coun t (P < 0.05). Each 10-year age group had a 2.4-fold difference in canc er risk (95% confidence interval, 1.9-3.2; P < 0.001). Four cases of c ancer occurred in patients at low risk (younger than 30 years of age, (1000 polyps; 3.3%). Conclusions: More adenomas and older age are asso ciated with a higher risk of colorectal cancer. However, cancer does o ccur in low-risk individuals and may be missed by surveillance, making alternatives to prophylactic surgery inadvisable.