Kaplan Meier survival analysis shows that low CYP2A6 (p = 0.001), CYP2D6 (p = 0.024), CYP2C8 (p = 0.013), CYP2E1 (p = 0.011), CYP26A1 (p < 0.0001) and high CYP2C9 (p = 0.034), CYP2C18 (p = 0.003), CYP26B1 (p = 0.026) and CYP17A1 (p = 0.049) mRNA expression, in the total patient cohort, was significantly associated with adverse breast cancer-specific survival (Figure 6). This evidence concerns the gene CYP2D6 and breast cancer.