Ribociclib-induced autoimmune-like hepatitis: a case report.

Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer represents the most prevalent subtype of breast cancer. Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, in combination with endocrine therapy (ET), have shown substantial benefits in improving progression-free survival and, for ribociclib, an overall survival advantage. Despite clinical benefits, ribociclib is associated with elevated liver enzymes and severe liver dysfunction. We present a 44-year-old Caucasian woman with HR-positive, HER2-negative metastatic breast cancer who developed drug-induced autoimmune-like hepatitis (DI-ALH) after ribociclib therapy. Initially treated for early-stage disease with surgery, chemotherapy, radiotherapy, and ET, she progressed to metastatic disease and received ribociclib, letrozole, and goserelin, achieving a partial response. Treatment was complicated by grade 3 hepatotoxicity, confirmed as DI-ALH by liver biopsy. Managed with prednisolone and azathioprine, ribociclib was reintroduced at a reduced dose and later escalated to full dose. This case report highlights the importance of a multidisciplinary approach to balance oncologic efficacy with hepatologic safety.