Liver toxicity with ribociclib in a patient with metastatic hormone receptor positive postmenopausal breast cancer

Introduction: In recent years, highly selective reversible CDK4/6 inhibitors have been combined with aromatase inhibitors for their efficacy and ease of application in the treatment of advanced stage of hormone-responsive breast cancers. Oral use of these drugs facilitates patient compliance. However, adverse drug reactions are reported due to these drugs, in the literature. Diverse adverse reactions such as skin reactions, liver toxicity, and vitiligo with ribociclib have been reported. Case report: In this study, we present of liver toxicity due to the use of ribociclib in a case of advanced breast cancer with metastases. It is noteworthy that the patient did not have any other concomitant disease and did not take any other medication. Management and outcome: After the 600 mg initial dose of ribociclib, neutropenia occurred at the beginning of the therapy, the dose was reduced to 400 mg, and liver enzymes started to rise in the second month of the therapy. In the fifth month of the intermittent treatment period, liver toxicity was grade 3. Discussion: Liver adverse reaction occurred due to ribociclib use in the patient who had no history of any other disease. The Naranjo algorithm score was evaluated as 9. Considering the excretion of ribociclib by sulfation, cysteine conjugation, and glucuronidation, which are phase II reactions, n-acetyl cysteine (NAC) treatment (600 mg/day) was started for the patient. NAC therapy is recommended to reduce elevated liver enzymes in the case. The patient's treatment has been continuing with palbociclib for 5 months. No increase in liver enzymes was observed.