Background: Body mass index is an established risk factor for postmenopausal breast cancer. Epidemiologic studies have also reported a positive association between type 2 diabetes (T2D) and breast cancer risk.
Methods: To investigate a genetic basis linking these common phenotypes with breast cancer, we tested 31 common variants for T2D and obesity in a case-control study of 1,915 breast cancer cases and 2,884 controls nested within the Multiethnic Cohort (MEC) study.
Results: Following adjustment for multiple tests, we found no significant association between any variant and breast cancer risk. Summary scores comprising the numbers of risk alleles for T2D and/or obesity were also not found to be significantly associated with breast cancer risk.
Conclusions: Our findings provide no evidence for association between established T2D and/or obesity risk variants and breast cancer risk among women of various ethnicities.
Impact: These results suggest that the potential for a shared biology between T2D/obesity and breast cancer is not due to pleiotropic effects of these risk variants.