Somatic Mutation Profiles in Colorectal Cancers Differ by Population

PURPOSE Colorectal cancer (CRC) incidence and mortality rates differ by population, and evidence suggests that genetic differences may affect cancer biology. However, studies investigating CRC variants in genetically heterogeneous populations are limited. Using somatic tumor mutation profiling of CRCs diagnosed in African Americans (AAs), Ghanaians, Ethiopians, and NHWs, we explore correlations between population group and population-specific tumor variants. PATIENTS AND METHODS Somatic DNA from CRC tumors resected from 150 individuals, including 43 AAs (27%), 53 NHWs (35%), 21 Ghanaians (14.2%), and 33 Ethiopians (22.3%), was sequenced on the Illumina NovaSeq platform, targeting 290 genes. We compared mutations in AAs, Ghanaians, and Ethiopians to those in NHWs to identify variants enriched in historically underrepresented groups. RESULTS US cohort tumors were diagnosed at significantly younger ages with more early-onset cases (<50 years old) than African cohorts (p <0.05). Significant differences were observed in primary tumor location, MMR phenotypes, KRAS mutations, and distribution of tumor mutational burden by population. BRAF V600E mutations were rare across all groups, while non-V600E BRAF mutation rates were higher in AA and NHW (43-44%) than Ethiopian and Ghanaian (14-33%) samples. Population-specific differences were identified in mutation rates of APC, CTNNB1, RNF43, PIK3CA, and TP53, as well as in pathogenic variant occurrence.