CYP2D6 and breast cancer: For these, a high level of evidence is fulfilled only by tamoxifen dosage adjustment for CYP2D6 haplotypes (CYP2D6*1, CYP2D6*10, CYP2D6*3, CYP2D6*4, CYP2D6*41, CYP2D6*5, and CYP2D6*6) in breast cancer.