Impact of Having a Second Degree Relative with Colorectal Cancer on the Risks of Developing Adenomas Kenny Chiu, Hyung Cho, Sharon Bayuga, Tim Church, Margaret Mandelson, Andrew Feld, John Allen, Glenn Mills, Paul Jordan, Michael O’Brien, Ann Zauber, Sidney Winawer Colon cancer screening studies have concentrated on studying the risks of 1 degree relatives (FDR) with colon cancer and under current screening guidelines, having affected 2 degree relatives (SDR) place a person in the average risk category. However, there is a small increase in colon cancer risks from having an affected SDR. The aim of this study is to evaluate how an affected SDR or FDR affect the prevalence of adenomas and advanced adenomas in a multicenter colon cancer screening trial. As part of the National Colonoscopy Study (NCS), 622 subjects enrolled from 1999 to 2002 underwent a screening colonoscopy. The presence of adenomas, their number, size, and location were recorded. All histologies were confirmed by an independent pathologist. The subjects were categorized as having an affected FDR, SDR, or neither. The endoscopists determined that 99.4% had a good preparation and the cecum was reached in 98.9%. Subjects with an affected FDR and those with an affected SDR show a similar trend towards an increased risk for adenomas. Having either an affected FDR or SDR increases the risk for adenomas when compared to those with neither (p Z 0.03). There was no difference in the ratio of right vs left sided adenomas or in their multiplicity based on family history. In conclusion, subjects with an affected SDR show a trend towards an increased risk for adenomas similar to those with an affected FDR. There is a statistically significant increase in the risk for adenomas in subjects with either an affected FDR or SDR. The number of advanced adenomas is too few to show a trend. The NCS is ongoing and will accrue a larger cohort to further evaluate the role of SDR’s in the risk of advanced adenomas. The impact of family histories is still being explored and with further studies, the presence of an affected SDR may place individuals in a higher risk screening category.