Abstract 3714: Detroit African Americans (AA) are overrepresented among patients with large high-grade dysplastic (HGD) adenomas (LHiGDA) versus those with small HGD adenomas (ShiGDA)
Authors: Tobi Martin , Antaki Fadi , Rambus MaryAnn , Sochacki Paula , Levi Edi 
Published: August 2015

Colorectal cancer incidence and mortality impacts African Americans more than other ethnic group. While causes for this disparity are likely multifactorial, etiology of carcinogenesis may be the most important. A better understanding of these factors might enable us to design interventions based on regional realities. In the context of screening trials we obtained data from a cohort of patients with high-grade dysplastic adenomas. We compared differences between those with large-sized (&gt;1cm) and those with smaller lesions. Methods: Patients were selected on the basis of high CRC risk based on a brief questionnaire. Prior to colonoscopy, stool was submitted for FOBT and anti-adenoma antibody (Adnab-9) binding determined by ELISA. The colonoscopy outcomes were noted for the cross-sectional element of the study. The longitudinal component enabled collection of additional specimens to elucidate the source of the adenoma antigen. Pathology was reviewed and antigenic mapping of 6 colonic segments was performed by Adnab-9 immunohistochemistry. If any 2 contiguous colonic segments expressed the antigen the colon was deemed to have a field effect. Results: 49 Patients were found to have HGD lesions of whom 26 were AA (53%). All but 1 were male. Mean age±SD was 62±14.8 years. 28 (57%) had LHiGDA and the remainder ShiGDA. 69% AA had LHiGDA versus 29% in the ShiGDA group (OR 5.9 CI 1.7-20.9;p = 0.03). Intragroup age differences between the AA and non-AA patients were not statistically (NSS) different (66.3±8.3 versus 63.9±10.5 and 58.4±21.9 versus 61.07±9.9 years respectively). Intergroup age variation by race was NSS (AA p = 0.2 and non-AA p = 0.5). Likewise intergroup lesion size variations were NSS (p = 0.4 and p = 0.2 respectively). The proportions of TVA were also NSS between the groups (p = 1 and p = 0.2 respectively}. The stool Adnab-9 binding was also not significantly different (p = 0.5 and p = 0.9 respectively). There was however a significant difference between the 2 lesion groups in terms of the presence of a field effect which was performed in a small percentage (14.3 versus 33%) for the large versus the small lesions (100 vs 14.3% RR7 CI 1.1-43;p&lt;0.02) but numbers were too small for intragroup calculations. Conclusions: AA are overrepresented in the LHiGDA group but there were no clues for differing pathways of carcinogenesis or for the differential dwell times of these lesions. We did not evaluate habits such as alcohol intake and smoking as risk factors which conceivably may play a role. The morphology of the lesion and pathway antigens suggest that the adenoma-carcinoma is the pathway of causation but these should be further studied to design effective intervention and screening. Screening is likely to better detect the large than the small lesions and this may be an advantage for the AA population who accordingly should be encouraged to actively participate in local screening programs.

Citation Format: Martin Tobi, Fadi Antaki, MaryAnn Rambus, Paula Sochacki, Edi Levi. Detroit African Americans (AA) are overrepresented among patients with large high-grade dysplastic (HGD) adenomas (LHiGDA) versus those with small HGD adenomas (ShiGDA). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3714. doi:10.1158/1538-7445.AM2015-3714