MTHFR C677T Polymorphism and Colorectal Cancer Risk in Asians, a Meta-analysis of 21 Studies

Background: Previous studies concerning the association between methylenetetrahydrofolate reductase(MTHFR) C677T polymorphism and colorectal cancer risk in Asian populations generated conflicting results.A meta-analysis was therefore performed to allow a more reliable estimate of any link.
Methods: Relevantstudies concerning the association between the MTHFR C677T polymorphism and risk of colorectal cancer wereincluded into this meta-analysis. The quality of the studies was assessed according to a predefined scale. Oddsratios (ORs) and 95% confidence intervals (CIs) were determined for this gene-disease association using fixedor random effect models according to the heterogeneity between included studies.
Results: Finally, 21 studieswith a total of 6692 cases and 8266 controls were included. Meta-analyses showed that there was an obviousassociation of the MTHFR 677T allele with decreased risk of colorectal cancer (OR = 0.91, 95%CI=0.85-0.98,P=0.011). Subgroup analyses by country further identified this association, with dietary folate as the main sourceof heterogeneity.
Conclusion: The MTHFR 677T allele is associated with a lower risk of colorectal cancer inAsian populations, and there is effect modification by population plasma folate.