Racial Differences in the Phenotype of Colorectal Cancer: A Prospective Comparison Between Nigeria and South Africa.

Introduction: There are significant differences in the phenotype of CRC by race in the U.S. A similar CRC phenotype-race relationship also appears to exist in South Africa (SA). However, there is a paucity of comparative data on the presentation and survival of CRC in sub-Saharan African by country of origin or race. This study compares clinicopathologic variables between CRC patients in Nigeria and SA.

Methods: From a prospective CRC database, consecutive patients diagnosed between September, 2013 and October, 2018 from the African Research Group for Oncology in South West Nigeria were compared to consecutive patients diagnosed from January, 2016 to October, 2018 from the Colorectal Cancer in South Africa database. Patients with histologically confirmed adenocarcinoma were included. Patients were excluded if they had in-situ disease or no histological diagnosis. Clinical outcomes were calculated from the date of presentation. National census categories were used to define self-reported race in SA.

Results: The mean age at presentation in Nigeria (n = 347) was 54.1 years (SD 15.5) compared to 56.8 (SD 13.7) in SA (n = 534). The median age among Black SA (BSA) patients was significantly lower than the median age among White SA (WSA) patients (55 vs. 63, p < 0.001). Right-sided colon cancer was more common in Nigerian (27.4%) and BSA (21.2%) patients compared to WSA patients (15.2%, p < 0.001). Nigerian (39.1%) and BSA (16.7%) patients were also more likely to present with mucinous histology than WSA patients (4.9%, p < 0.001). There was a significant difference in the stage-at-presentation between the cohorts, with a large burden of stage IV disease in the Nigerian cohort (52.6%). Adjusting for stage-at-presentation, there was a significant difference in the median overall survival between country and racial cohorts.

Conclusion: There are significant differences in the phenotype of CRC between Nigeria and SA. Nigerian and BSA patients, appear to share characteristics that are different than those of WSA patients. Larger series with tissue banking and next-generation sequencing are needed to better delineate these observed differences.