A significant correlation was observed between the CYP2C9*2 polymorphism and chemotherapy resistance (OR = 4.64; CI 95% = 1.01 - 20.91), as well as between CYP2C9*2 heterozygotes and chemotherapy resistance in women with nodal forms of breast cancer and a cancer hereditary load (OR = 15.50; CI 95% = 1.08 - 826.12) when the potential combined effects were examined.
We examined 3 examples: (1) BRCA1/2 testing for breast cancer risk, (2) HER2/neu overexpression testing to guide drug treatment in women with breast cancer, and (3) CYP2C9 testing before the use of the anticoagulant warfarin.