CYP2D6 and breast cancer: A meta-analysis of data obtained from 4973 tamoxifen-treated patients with breast cancer in retrospective studies (12 globally distributed sites) suggested that strict eligibility criteria (DNA source and target alleles for CYP2D6 genotyping, menopausal status, ER status, dose of tamoxifen and periods of tamoxifen dosing) are needed to assess the CYP2D6 status and clinical outcomes in tamoxifen adjuvant therapy (Ref.