Molecular Epidemiology of Colorectal Cancer in Nigeria: KRAS and BRAF Mutation Profiling Across Geopolitical Zones

Colorectal cancer (CRC) incidence is rising in Nigeria, yet molecular epidemiological data critical for targeted therapy and population risk stratification are entirely absent from Nigerian literature. This study profiles KRAS and BRAF mutation frequencies in CRC across Nigeria's six geopolitical zones to characterize the molecular landscape of CRC in the Nigerian population and assess implications for precision oncology. A prospective multicentre study recruited 240 patients with histologically confirmed CRC from six tertiary hospitals representing each geopolitical zone between 2020 and 2024. Formalin-fixed paraffin-embedded tumour tissue underwent allele-specific PCR and Sanger sequencing for KRAS exons 2 to 4 and BRAF V600E mutation analysis. Clinicopathological and outcome data were correlated with mutation profiles. KRAS mutations were identified in 43% of cases, with codon 12 mutations predominating. BRAF V600E was present in 8.3% of cases. KRAS mutation frequency varied significantly by geopolitical zone, with the South East showing the highest prevalence (52%). Female sex and right-sided colon tumours were significantly associated with BRAF mutation. KRAS-mutant patients had inferior disease-free survival on standard chemotherapy. This study provides the first geographically stratified molecular profile of CRC in Nigeria, establishing a foundation for precision medicine approaches and recommending routine molecular testing as a standard of care at Nigerian tertiary oncology centers. Keywords: colorectal cancer, KRAS, BRAF, molecular epidemiology, Nigeria