Toxic hepatitis in metastatic breast cancer patient using ribociclib and denosumab

Introduction Hepatotoxicity is observed due to cyclin-dependent kinase (CDK4/6) inhibitors used to treat hormone receptor-positive metastatic breast cancer. However, it should not be ignored that denosumab may be hepatotoxic, although it is rare. Case Report: A 73-year-old female patient with breast cancer with axillary lymph node, adrenal gland and bone metastases was started on ribociclib letrozole and denosumab treatment. Ribociclib treatment was discontinued due to grade 4 hepatotoxicity during treatment, but liver function tests did not decrease. After discontinuation of denosumab treatment, alanine aminotransferase and aspartate aminotransferase values regressed to baseline values. Management and Outcome: Despite the discontinuation of ribociclib treatment, other causes of liver toxicity were investigated due to persistence of hepatic transaminases and elevation. Autoimmune hepatitis markers were negative. Hepatobiliary USG did not reveal any pathological findings except hepatosteatosis. Liver biopsy was performed to determine the etiology. Pathology result was compatible with acute hepatocellular damage (in favor of toxic hepatitis). A decrease in liver values was detected after discontinuation of denosumab treatment. Discussion: Although cases with improvement in liver enzymes have been reported after discontinuation of ribociclib, no improvement in hepatotoxicity was observed in our case. Since the liver biopsy was toxic hepatitis, it was thought that other drugs used by the patient might cause this toxicity, and a significant decrease was observed in liver values after discontinuation of denosumab. Denosumab-induced liver toxicity is very rare, and there are only a limited number of cases in the literature.