Reduced breast cancer risk with increasing serum folate in a case-control study of the C677T genotype of the methylenetetrahydrofolate reductase gene.

Breast cancer risk may be associated with folate status or the C677T genotype of the methylenetetrahydrofolate reductase (MTHFR) gene. We compared serum folate concentrations and C677T genotype in 141 breast cancer patients and 109 age-matched controls. Serum folate was significantly lower in cases compared to controls (geometric means, 5.7 versus 6.6 microg/l; P=0.005). Breast cancer risk was not associated with C677T genotype. After adjusting for age of menarche, parity, alcohol intake and total fat intake we observed reductions in odds ratios for breast cancer risk comparing the highest with the lowest quartiles of serum folate concentrations of 0.23 (95% confidence interval (CI) 0.09, 0.54) for the entire group, 0.27 (CI 0.09, 0.80) for the wild-type and 0.08 (CI 0.01, 0.52) for the heterozygous C677T genotype. We conclude that for the whole group, and the wild-type and heterozygous C677T genotypes, increased serum concentrations of folate were associated with reduced risks of breast cancer.