Implementation of Universal Colorectal Cancer Screening for Lynch Syndrome in Hispanics Living in Puerto Rico

OBJECTIVE

Colorectal cancer is the leading cause of cancer death in Puerto Rico and third among Hispanics in the USA. Up to 2-4% of colorectal cancer cases are a result of Lynch syndrome (LS), a hereditary cancer syndrome caused by a germline mutation in at least one of the DNA mismatch repair genes. The objective of this study was to determine the prevalence of LS in colorectal tumors during the first 15-months after the implementation of universal tumor-based screening for LS in Puerto Rico.

METHODS

A total of 317 colorectal tumors were evaluated in a large private pathology laboratory from September 2014 to December 2015. Clinical characteristics were obtained from the pathology reports. Unadjusted and adjusted logistic regression models were used to estimate the magnitude of association (odds ratio [OR] with 95% confidence intervals [CI]) between absent MMR protein expression and patient characteristics.

RESULTS

Most cases (93.4%) were analyzed by immunohistochemistry; 11.8% (35 of 296) had deficient mismatch repair protein expression. While 29 of the 317 cases were subjected to PCR-based microsatellite instability analysis of which 10.3% (3 of 317) had microsatellite instability. In total, 11.0% of the tumors were reported MMR deficient. These tumors were more likely from females and more likely localized in the proximal colon compared to those with proficient MMR expression.

CONCLUSIONS

Our data is consistent with the results from other studies including US Hispanics, where approximately 10% of Hispanic individuals with colorectal cancer have microsatellite instability. Our results support universal tumor-based screening for LS among Hispanics in accordance with National Comprehensive Cancer Network guidelines.

Association of genetic ancestry with colorectal tumor location in Puerto Rican Latinos

Background

Colorectal cancer (CRC) is the first cause of cancer deaths among Puerto Ricans. The incidence and mortality of CRC in Puerto Rico continue to be on the rise. The burden of CRC in Puerto Rico is higher than among US Hispanics and is second only to African Americans, thus supporting the importance of studying this CRC health disparity. The genetic background of the Puerto Rican population is a mix of European, African, and Amerindian races, which may account, in part, for the differences observed in the CRC mortality rates among Puerto Ricans. The objective of the study was to assess the role of genetic ancestry in CRC risk and its association with clinicopathological features of CRC tumors in Puerto Ricans.

Results

We used a validated panel of 105 ancestry informative markers (AIMs) to estimate genetic ancestry in 406 Puerto Rican CRC cases and 425 Puerto Rican controls. We examined the association of genetic ancestry with CRC risk and tumor clinicopathological characteristics.

Conclusions

The mean ancestry proportions in the study population were 61% European, 21% African, and 18% Amerindian. No association was observed between genetic ancestry and risk of CRC. However, African ancestry was associated with an increased risk of developing rectal tumors (OR = 1.55, 95% CI 1.04–2.31). Additional studies are needed to fully elucidate the role of African ancestry in CRC carcinogenesis.

Abstract B35: Molecular characterization of colorectal tumors from Puerto Rican Hispanic patients

Background and Objectives: Accumulating evidence supports that colorectal cancer (CRC) is comprised of different genetic diseases affecting the same organ. The molecular classification of CRC is evolving as we gain a comprehensive knowledge about the mechanisms and processes resulting in colorectal carcinogenesis. Tumors display distinct characteristics depending on the molecular subtype, which may affect response to treatment, prognosis, and survival. CRC is the leading cause of cancer deaths among Puerto Rican Hispanics (PRH). The aim of this study was to characterize colorectal tumors at a molecular level in a cohort of PRH in order to determine the prevalence of molecular markers.

Methods: The molecular markers evaluated were microsatellite instability (MSI), CpG island methylation phenotype (CIMP), and mutations in KRAS and BRAF oncogenes. In addition, HPV infection status was assessed, as it has been associated with CRC. Sociodemographic and clinicopathological characteristics were evaluated according to MSI, CIMP, KRAS/BRAF mutation and HPV-status using Pearson's Chi-Square and Mann-Whitney U-test.

Results: A total of 201 CRC tumors were included in our study. Of the evaluated tumors 2.6% (n=3) showed MSI and 1.8% of the studied tumors had CIMP high phenotype (n=2). The incidence of KRAS and BRAF mutations for our study was 30.6% (n= 38) and 9.2% (n=11), respectively. Furthermore, KRAS positive individuals were more likely to have private or Medicare insurance (p=0.017). In addition, BRAF mutation-positive tumor were more likely to be poorly differentiated when compared to BRAF mutation-negative tumors (p=0.009). HPV infection was not associated with any molecular characteristics examined.

Conclusions: We present for the first time the molecular characterization of CRC tumors in PRH. The observation of a different molecular signature for the CRC tumors (low MSI, CIMP Zero and mainly wild-type for KRAS and BRAF) suggests that CRC in this population might be driven by additional genetic, epigenetic and environmental factors than other racial/ethnic groups.

Citation Format: Yaritza Díaz-Algorri, Julyann Pérez-Mayoral, Maria González-Pons, Natalia Rodríguez, Belisa Suárez, Giancarlo Colón, Javier Sevilla, Daphne L. Jorge, Xavier Llor, Rosa Xicola, Luis Tous, José S. Reyes, Marla Torres, Ajay Goel, Segundo Rodriguez, Marcia Cruz-Correa. Molecular characterization of colorectal tumors from Puerto Rican Hispanic patients. [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 B35.