Abstract B85: Racial differences in the risk of serrated polyps and conventional adenomas in a younger aged, uninsured population in South Carolina
Authors: Wallace Kristin , Alberg Anthony , Blankenship Bridgette , Brandt Heather , Caldwell Renay , Dunn James , Hegedus Patricia , Hoffman Brenda , Marsh Courtney , Seabrook March , Stinson Marylou , Thibault Annie , Berger Franklin 
Published: October 2015

Compared to European Americans (EA), African Americans (AA) have higher colorectal cancer (CRC) incidence and are diagnosed with CRC at younger ages. The reasons for these disparities are poorly understood, but one contributing factor could be reduced access to high-quality preventative care. To address CRC disparities, this study assessed whether a racial difference in risk of large bowel polyps (precursors to most CRC) persists within a younger-aged, uninsured population in South Carolina (SC) undergoing screening colonscopy. We analyzed data from a multi-site statewide CRC screening program in SC to explore the risk of large bowel polyps among AA and EA. Eligible patients were uninsured, asymptomatic, had no personal history of colorectal neoplasia, and were between the ages 45-64 years (AA) or 50-64 years (EA). Using generalized linear regression, we estimated risk ratios and 95% confidence intervals (CI) as measures of the association between race and risk for one or more conventional adenomas or serrated polyps adjusting for age, sex, family history of CRC, and clinical site. Serrated polyps (SP) were defined as one or more hyperplastic polyps, sessile serrated adenomas, traditional serrated adenomas, and mixed adenomatous polyps. SP were first classified in a single category since not all project pathologists used up-to-date pathologic terminology and there was a high-level of variability among clinical sites in use of newer SP categories (i.e., sessile, traditional adenomas). Serrated adenomas included any SP with serrated adenomatous features (sessile, traditional, or mixed). Advanced SP were defined as SP with large size (an estimated ≥ 1 cm). Conventional adenomas (CA) were defined as tubular, tubulovillous, or villous polyps. Advanced CA were defined as adenomas with at least 25% villous component (TVA), high-grade dysplasia (HGD), or large size. We also stratified polyps separately according to colonic region (proximal or distal colorectum), large size, and advanced CA histology (TVA, HGD). Of the 237 subjects enrolled (127 AA, 91 EA, 19 other), 233 had a complete exam (i.e., to the cecum). Our results suggested a lower risk of SP among AA compared to EA: any SP (RR 0.50 (95% CI 0.30-0.84)), any serrated adenoma (RR 0.35 (95% CI 0.11-1.14)), and any large SP (RR 0.27 (95% CI 0.09-0.85)). Although not always statistically significant, the trend in the results indicate that the risk of CA was higher in AA compared to EA: any CA 1.17 (95% CI 0.77-1.79), large CA 2.16 (95% CI 0.70-6.66), proximal large CA 4.24 (95% CI 1.0-18.01), and any advanced CA 1.38 (95% CI 0.55-3.42). In patients under 55 years of age (median age), AA compared to EA had higher risk of advanced CA histology lesions RR 4.11 (95% 1.05 -16.11), but otherwise risks were similar in the age groups. Overall, our findings suggest that it is important to consider type of polyp and age when assessing risk in different racial groups. Our results in this unique study population are consistent with an earlier study showing that AA have a lower risk of metachronous SP and among younger patients, an increased risk of conventional adenomas, especially advanced lesions. The persistence of these observations within a study population comprised of all medically underserved individuals implies that the unique features of the epidemiology of colorectal neoplasia in AA cannot be completely attributed to access to care barriers.

Citation Format: Kristin Wallace, Anthony Alberg, Bridgette Blankenship, Heather Brandt, Renay Caldwell, James Dunn, Patricia Hegedus, Brenda Hoffman, Courtney Marsh, March Seabrook, Marylou Stinson, Annie Thibault, Franklin Berger. Racial differences in the risk of serrated polyps and conventional adenomas in a younger aged, uninsured population in South Carolina. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B85.