Microsatellite Instability and Life Style Factors in Sporadic Colorectal Cancer

BACKGROUND: Colorectal cancer (CRC) in Egypt is a relatively high young onset disease. As a form of heterogeneous cancer, there is interplay between genetic and environmental factors. We aimed at probing the association of life style factors and Microsatellite Instability (MSI) status that could provide more insights on carcinogenic process of CRC. METHODS: One hundred incident sporadic CRC patients were involved. Information on risk factors of CRC was obtained and microsatellite instability status was predicted through evaluation of MMR protein expression via immunohistochemistry (IHC). RESULTS: Median age was 47.50 years, females represented 54.0% and 36% of patients were Microsatellite Instability High (MSI-H). Most patients with right sided colon cancer (78.3%) were MSI-H while mostly stable or low MSS/MSI-L for left-sided colon and rectum (78.6%, 74.3% respectively, p<0.001). Patients with low physical activity had higher risk of MSS/MSI-L than those with moderate or high activity p =0.026. Patients with BMI greater than 30 Kg/m(2) had higher MSS/MSI-L (75.5%) than those with BMI between 25-30 Kg/m(2) (60.6%) and those with normal BMI <25 (38.9%), p for trend = 0.006. On subgroup analyses, the association of high BMI with MSS/MSI-L was only shown in patients younger than 40 years, females, stage III, non-mucin secreting adenocarcinoma and a significant interaction with physical activity. CONCLUSION: In Conclusion, the present study confirms the increased risk of MSS/MSI-L with increased BMI and speculates this association to be modified by patient’s life style and tumor characteristics. Further research is needed to validate present results.