Abstracts
1998 Digestive Disease Week

#998

ATTENUATED FAMILIAL ADENOMATOUS POLYPOSIS: ASSOCIATION OF AGE AND POLYP CHARACTERISTICS WITH COLORECTAL CANCER,. D.R. Adams, C.A. Ternent, K.M. Lin, P. Watson, A.G. Thorson, G.J. Blatchford, M.A. Christensen, H.T. Lynch, Departments of Surgery and Preventive Medicine, Creighton University School of Medicine, Omaha, NE.

The purpose of this study was to analyze characteristics of colon polyps in attenuated familial adenomatous polyposis (AFAP) with respect to colorectal cancer(CRC) risk. Detailed endoscopy and cancer data of 44 proven AFAP gene carriers and 11 obligate AFAP gene carriers were analyzed. Mean ages of polyp and CRC diagnosis were compared and average annual and cumulative risk of polyp development to age 73 were determined. Endoscopy data was analyzed to compare the size and location of benign versus malignant colorectal lesions. Mean ages of colon polyp diagnosis and CRC diagnosis were 40 (range: 14-73) years and 54 (range: 31-85) years, respectively (p=0.005). Average annual risk of polyp development was 2.9%. Cumulative risk of colorectal polyp development to age 73 was 90%. Mean size of benign colon polyps was 3mm compared to 32mm for malignant lesions (p<0.001). Colorectal polyp versus cancer distributions for the right (59% vs 19%), transverse (19% vs 19%), left (20% vs 35%) and rectum (2% vs 26%) were significantly different (p<0.00001). Colorectal polyps in AFAP are diagnosed at a mean of 14 years prior to diagnosis of CRC. Cumulative lifetime risk for colorectal polyps shows a near complete penetrance by age 73. CRC in AFAP is associated with a tenfold increase in the size of colonic lesions. In spite of a right sided predominance of colorectal polyps in AFAP, colorectal cancers do not appear to follow a similar distribution.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.