A Case of Breast Cancer Treated with Adjuvant Chemotherapy in a Patient Receiving Tacrolimus Medication after Liver Transplantation

: Tacrolimus is a calcineurin inhibitor that has been used to prevent allograft rejection after organ transplantation. We report the case of a living-donor liver transplant recipient with breast cancer who received adjuvant chemotherapy at an appropriate relative dose intensity in spite of a decrease in the trough blood concentration of tacrolimus. The patient was a woman in her 50s who had undergone living-donor liver transplantation because of primary biliary cirrhosis and received maintenance therapy consisting of tacrolimus. She was diagnosed as having locally advanced breast cancer(ER and HER2 positive). After surgery, we administered 4 courses of EC followed by weekly administration of paclitaxel plus trastuzumab. During chemotherapy, although the trough blood concentration of tacrolimus was slightly decreased, neither severe adverse event nor allograft rejection was observed. Recently, organ transplantation outcomes have significantly improved as a result of the progress of immunosuppressive agents. However, the development of malignancies after transplantation is a serious problem.