Introduction: The association between high bone mass and increased breast cancer risk has been established. Identification of polymorphisms and the resultant variant receptors suggests the possibility of differential effects on hormone responsive genes when complexed with the hormones. Both estrogen receptor-alpha (ER) and vitamin D receptor (VDR) polymorphisms have been associated with bone density. Thus, we examined these polymorphisms for association with increased breast cancer risk among US African-American and white women.
Methods: A case-control study was conducted to measure ER and VDR polymorphisms and radial bone mineral density (BMD) in African-American and white women, and to examine the association between polymorphisms, bone density and breast cancer risk. Genotypes and bone density were obtained from 412 women (220 cases and 192 controls, with equal distribution between the two ethnic groups).
Results: We found no evidence for an association between either the ER or VDR genotypes and breast cancer risk. Also, there was no difference in the risk of breast cancer by genotypes after adjusting for ethnicity. The addition of age, sex and ethnicity-specific BMD (Z-scores) did not significantly change the odds ratio for breast cancer.
Conclusions: Our data suggest that the polymorphisms investigated had no effect on risk of breast cancer in this population. Thus, we found no evidence to support our hypothesis that breast cancer cases and controls would have a different distribution of ER and VDR genotypes. Furthermore, the polymorphisms were not associated with differences in bone mass and its relationship with breast cancer risk.