Studies have indicated that polymorphisms of CYP2D6 imposed an increased risk of breast cancer and esophageal squamous cell carcinoma in those people with a family history of cancers.43, 44 Zienolddiny S et al found that CYP2D6 and CYP1B1 increased genetic susceptibility to NSCLC.45 In addition, Lee JY et al showed that hydroxychloroquine metabolism was related to CYP2D6 rs1065852 polymorphisms.46 This evidence concerns the gene CYP2D6 and breast cancer.