CYP1B1 and breast cancer: None of the previously published studies on the CYP1B1 Asn453Ser polymorphism and breast cancer conducted among average-risk women reported an increase in risk of breast cancer associated with this polymorphism [35-38], including a recent meta-analysis that reported an OR of 0.91 (95% CI 0.79, 1.04) associated with the heterozygous Asn/Ser genotype and an OR of 0.85 (95% CI 0.54, 1.34) associated with the homozygous Ser/Ser genotype [39].