Genetic and environmental determinants on tissue response to in vitro carcinogen exposure and risk of breast cancer.

To test the hypothesis that individual susceptibility to carcinogen exposure is a risk factor for breast cancer, we measured DNA adduct formation in normal breast tissues treated in vitro with 4 micro M benzo(a)pyrene in 76 cancer cases and 60 noncancer controls. We found a significantly higher level of adducts (134.6 +/- 21.2/10(9)) among cases compared with controls (66.9 +/- 7.5; P = 0.007). The level of adducts was significantly associated with the risk of breast cancer (odds ratio, 4.38; 95% confidence interval, 1.04 to 18.50; P = 0.044) after adjusting for confounders. Stratified analysis and regression analysis demonstrated that race, pack-years of smoking, family history of breast cancer, and CYP1B1 genotype were significant predictors of the level of benzo(a)pyrene-induced adducts in the breast tissues. These observations suggest that genetic susceptibility to carcinogen exposure may play an important role in breast carcinogenesis.