Relationship Between ABO Blood Group and Microsatellite Instability in Colorectal Cancer: A Retrospective Single-Center Study.

PURPOSE: Colorectal cancer (CRC) is the second most common cancer in both women and men. Microsatellite instability-high (MSI-H) CRC is a molecular subgroup and has distinct clinical and pathologic features from microsatellite stable (MSS) CRC. Studies have suggested an association between hereditary antigens in ABO blood group system and the risk of developing various cancers but the relationship between blood groups and MSI-H CRC has not been investigated. This study aimed to investigate this relationship and its possible effect on clinicopathological features in patients with CRC. METHODS: This is a retrospective cross-sectional single-center study including pathology-confirmed CRC patients. Demographic and clinicopathological features, blood groups, and microsatellite status were examined among two groups. Microsatellite instability was examined by immunohistochemistry (IHC) in pathology specimen. RESULTS: A total of 144 patients, 72 patients with MSI-H CRC and 72 patients with MSS CRC, were included in the study. Among all patients, median age was 61.7 ± 12.9 (range 27-89) and 57.6% were male. MSI-H and MSS groups were similar in terms of age, gender distribution, and comorbidities. Patients with MSI-H CRC had significantly common O-blood group than control group (44.4% vs 18.1%, p: 0.001). In multivariate analysis, O-blood group was 4.2 times more common in the MSI-H patient group (95% CI: 1.514-11.819, p: 0.006). Also patients with MSI-H CRC were found to have significantly more right-sided, high-grade tumors and early-stage disease. CONCLUSIONS: MSI-H CRC is an important subgroup in colon cancer with different molecular and clinicopathological features. It was observed that O-blood group was 4.2 times more common in MSI-H CRC. We believe that clarifying the relationship between microsatellite instability and O-blood group and its possible genetic and epigenetic mechanisms in larger studies will enable us to better understand tumor behavior and prognosis, also affect our treatment choices of these patient groups.