In stratification analysis for different genotypes of the four SNPs in CYP1A2 and CYP3A4, the Kaplan–Meier survival curve showed a significant association between the CYP1A2 rs2470890 polymorphism and OS among the 459 study breast cancer patients (P < 0.001, Figure 3A). Here, CYP1A2 is linked to breast cancer.