The MTHFR C677T polymorphism, estrogen exposure and breast cancer risk:: A nested case-control study in Taiwan

Background: We evaluated the effects of the MTHFR C677T polymorphism and its interaction with estrogen exposure on breast cancer risk in a nested case control study conducted in Taiwan. Materials and Methods: A total of 88 histologically confirmed breast cancer cases and 344 cancer-ftee controls were recruited between July 1992 and December 2000. The MTHFR C677T genotype was determined by a PCR-RFLP-based assay. All subjects completed in-person interviews. Results: There was a significant trend of breast cancer in relation to prolonged exposure to estrogens prior to the first full-term pregnancy (FFTP)(p for trend=0.0015). In contrast, there was no statistically significant associatiOn between the risk of breast cancer and the MTHFR C677T genotype. However, a significantly elevated risk of breast cancer predisposed by the MTHFR 677T variant genotype (CT and TT) was observed in women With prolonged exposure to estrogens prior to FFTP (adjusted OR=4.98, 95% CI=2.00-12.43).Conclusion: The results of this study suggest that the MTHFR 677T variant genotype pet, se may have no overall association with breast cancer risk.. but a sizable association could be observed in the presence of relevant environmental exposure.