Abstract A17: Molecular and clinicopathological features of native Nigerian colorectal cancer

Colorectal cancer (CRC) needs no introduction in Africa; once a rare cancer type, it is now the 3rd or 4th most common cancer. However, there are significant differences in the incidence rates, tumor biology, and clinical behavior in comparison to other populations. While the total incidence rates are about one-tenth of those in the developed world, Nigerian CRC occurs at a younger age and rapidly metastasizes. Molecular pathology and genetics of African CRC have not been comprehensively studied. In addition to better understanding of the biology of African CRC, analysis of genetic and molecular biomarkers, including microsatellite instability (MSI), is aimed at improving CRC diagnosis, treatment, and prognosis in Africa. We obtained 83 CRC paraffin-embedded blocks from the University of Ibadan and private pathology laboratories in Ibadan collected in the period from 2007 to 2014. Median age of the cases was 56±14.6 years with equal number of males and females. More than 60% of the patients had stage III and IV CRC. The majority were adenocarcinomas (76%) with a relatively high prevalence of mucinous adenocarcinoma (10%) and signet ring carcinoma (4%). Of all patients, 66% had rectal cancer. Poorly differentiated tumors were observed in 34% of all cases. We found a high prevalence of MSI CRC (43%, 15/35) in the tested Nigerian samples. There were no significant differences in clinicopathological features, including tumor location, between MSI and microsatellite stable (MSS) CRC. Our results are in line with our previous report that found a high prevalence (41%) of MSI CRC in Ghanaian patients. These findings raise important questions about the role of genetic and environmental factors in CRC development in West Africa. Citation Format: David O. Irabor, Marilena Melas, Stephen B. Gruber, Chanjuan Shi, Leon Raskin. Molecular and clinicopathological features of native Nigerian colorectal cancer [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr A17.