Elucidation of the molecular and clinical impact of microsatellite instability in Brazilian colorectal cancer patients at Barretos Cancer Hospital.

e23185Background: Colorectal cancer (CRC) has a high incidence and mortality in the world and in Brazil. The microsatellite instability (MSI) pathway is associated with a distinct mutational profile, which affects MSI target genes contributing to a different clinical impact. Reports have suggested that CRC aspects may be influenced by patients’ ancestry. This study aims to elucidate the molecular and clinical impact of MSI, and to determine Brazilian patients’ genetic ancestry. Methods: We enrolled 1013 patients. MSI was evaluated by molecular analysis, and MSI-H cases were further analyzed for alterations in 24 MSI-target genes, BRAF V600E, and MLH1 methylation. Genetic ancestry was evaluated by an AIMs panel. Results: MSI-H was observed in 10.5% of the cases. MSI-H cases were significantly associated with: right colon localization, staging II, absence of metastasis, mucinous histological type, III/undifferentiated histological grade, presence of synchronic tumor, no disease recurrence, and complete cure...