Dietary folate and vitamin B12 intake before diagnosis decreases gastric cancer mortality risk among susceptible MTHFR 677TT carriers.

OBJECTIVE: To assess gastric cancer survival in relation to dietary intake of methyl donors and the methylenetetrahydrofolate reductase 677C>T (MTHFR 677C>T) polymorphism. METHODS: A prospective cohort of 257 incidental, histologically confirmed gastric cancer cases was assembled in January 2004 and followed until June 2006. Patients were recruited from the main oncology and/or gastroenterology units in Mexico City and were queried regarding their sociodemographic information, clinical history, and dietary habits 3 y before the onset of their symptoms. The intake of methyl donors was estimated with a food-frequency questionnaire and the MTHFR 677C>T polymorphisms were determined by polymerase chain reaction/restriction fragment length polymorphism analysis. Cox's multivariate regression models were used to estimate the mortality risk of gastric cancer. RESULTS: MTHFR 677TT carriers with low folate and vitamin B12 intakes had the lowest survival rate in cases of gastric cancer. High intakes of folate and vitamin B12 before diagnosis was associated with decreased gastric cancer mortality risk in susceptible MTHFR 677TT carriers (mortality risk for folate 0.14, 95% confidence interval 0.04-0.46, P for trend=0.001; mortality risk for vitamin B12 0.23, 95% confidence interval 0.08-0.66, P for trend=0.008). CONCLUSION: Folate and related B vitamins may be used as an intervention strategy to improve the survival outcome of gastric cancer.