Abstract C34: Association of genetic ancestry with colorectal tumor characteristics in Puerto Rican Hispanics
Authors: Pérez-Mayoral Julyann , Soto Marievelisse , González-Pons Maria , Suárez Belisa , Olivera Myrta I. , Shah Ebony , Kittles Rick , Cruz-Correa Marcia R. 
Published: May 2016

Background: Colorectal cancer (CRC) is the 1st cause of cancer deaths in Puerto Rican Hispanics (PRH). Even though PRH have a lower incidence of CRC, when compared to other ethnic groups, their mortality rates are higher. As the 2nd largest Hispanic population on the United States, the increased CRC mortality rates for this ethnic group have a large socio-economic burden. The CRC epidemiologic data supports the importance of studying this cancer as a health disparity in PRH. The genetic background of the Puerto Rican population, which is mix of European, African and Amerindian races, could account, at least in part, for the differences observed in the CRC mortality rates for this population. The objective of this project was to assess the role of genetic ancestry in CRC risk and clinicopathological features of CRC tumors in the PRH population.

Methods: We used a panel of 105 ancestry informative markers (AIMs) to estimate genetic ancestry in 224 PRH CRC cases and 202 PRH controls. Additionally, we examined the association of genetic ancestry estimates with CRC risk and clinicopathological characteristics of CRC tumors in our study population using the Bayesian Markov Chain Monte Carlo method implemented in the software STRUCTURE. Logistic regression analysis was used to determine the association of genetic ancestry with disease risk. Pearson's Chi-Square and Fisher's Exact Test was used to determine the association of categorical values of genetic ancestry with tumor clinicopathological characteristics.

Results: Our results showed that the genetic ancestry mean estimates for the PRH population were 60% for European, 21% for African and 19% for Amerindian. No association of genetic ancestry with CRC risk in the PRH population was found in our study (OR= 0.86 [0.43-1.69], p=0.655). However, genetic ancestry was found to have a significant role on the CRC tumor characteristics of the studied population. High African ancestry (&gt;21.0%) was associated with distal tumor location, when compared to low African ancestry (≤ 21.0%) (p=0.012). Furthermore, low Amerindian ancestry (≤ 19.2%) was associated with poorly differentiated tumors (p= 0.022).

Conclusion: The preliminary results presented in this study show that genetic ancestry is associated with tumor location and differentiation, both associated with CRC prognosis. Additional studies are needed to fully elucidate the role of genetic ancestry in CRC susceptibility and prognosis.

Citation Format: Julyann Pérez-Mayoral, Marievelisse Soto, Maria González-Pons, Belisa Suárez, Myrta I. Olivera, Ebony Shah, Rick Kittles, Marcia R. Cruz-Correa. Association of genetic ancestry with colorectal tumor characteristics in Puerto Rican Hispanics. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C34.