A Meta-Analysis: Methylenetetrahydrofolate Reductase C677T Polymorphism in Gastric Cancer Patients Treated with 5-Fu Based Chemotherapy Predicts Serious Hematologic Toxicity but Not Prognosis

5-fluorouracil (5-Fu) metabolism associated enzyme, methylenetetrahydrofolate reductase (MTHFR)'s polymorphism C677T can affect enzyme activity and a series of studies have been performed to examine the association of this MTHFR polymorphism with the clinical outcomes of gastric cancer (GC) patients treated with 5-Fu based chemotherapies. However, the results are inconsistent and inconclusive. Therefore, a more comprehensive summary like meta-analysis on this topic is needed. We performed a systematic literature search of PubMed and Embase up to May 20, 2017. Researches exploring MTHFR polymorphisms C677T's relationship with the clinical outcomes (response rate, overall survival and toxicity) of GC patients treated with 5-Fu based chemotherapy were included. The association was measured by odds ratios (ORs) or hazard ratios (HRs) combined with their 95% confidence intervals (CIs) using random/fixed effects model according to the studies' heterogeneity. Subgroup, sensitivity and publication bias analyses were conducted. Thirteen studies were finally included in this meta-analysis. No significant association was found between response rate [TT/ (CC+CT) OR=1.31, 95% CI: 0.62-2.76] or overall survival [(CT+TT)/CC HR=1.05, 95% CI: 0.86-1.26; TT/(CT+CC) HR=1.48, 95% CI: 0.53-4.15] and MTHFR polymorphism C677T. However, GC patients with CC or CT genotype tended to experience less severe hematologic toxicity than those with TT genotype [(CC+CT)/TT OR=0.66, 95% CI: 0.48-0.91]. In conclusion, MTHFR C677T polymorphism predicts severe hematologic toxicity in GC patients receiving 5-Fu based chemotherapy, but not the efficiency.