Dalpiciclib induced hepatitis B virus reactivation leading to liver failure: a rare case report and review of the literature.

Dalpiciclib is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor that plays a key role in hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER-2)-negative breast cancer. However, there have been no reports of acute liver failure in Hepatitis B virus (HBV) carriers caused by HBV reactivation induced by dalpiciclib. We present a 50-year-old female with recurrent breast cancer and a history of asymptomatic HBV carriage. After dalpiciclib initiation, she developed progressive liver impairment, with hepatitis B virus DNA (HBV DNA) escalating from 1.02 × 103 to 2.13 × 106 IU/ml and HBeAg seroconversion from negative to positive, confirming HBV reactivation. Notably, the patient received initial dalpiciclib-based therapy at an external hospital, where antiviral prophylaxis was not initiated despite the availability of baseline HBV serological and viral load data, due to the failure to conduct clinical risk stratification for HBV reactivation based on these results-a critical gap in pre-therapy assessment for HBV-related risk stratification. Entecavir antiviral therapy led to suppressed viral replication and improved liver function during follow-up. This case emphasizes the need for HBV screening and close monitoring of viral markers/liver function in asymptomatic HBV carriers receiving dalpiciclib, as early antiviral intervention prevents severe liver complications. It also highlights the importance of clinical pharmacist-led medication follow-up management for outpatients receiving targeted anticancer therapy to avoid oversight of comorbidities and associated prophylactic treatment.