Late-Onset Immune-Mediated Hepatotoxicity Induced by the Immune Checkpoint Inhibitor Pembrolizumab in Lung Cancer: A Case Report

Lung cancer (LC) remains the leading cause of cancer-related death worldwide. The introduction of immune checkpoint inhibitors, such as pembrolizumab, has improved survival in selected patients. However, these therapies may cause immune-mediated adverse events, including hepatotoxicity, which poses a diagnostic challenge due to its low incidence and nonspecific presentation. We report a case of a patient with LC who developed persistent elevation of liver enzymes after 17 cycles of pembrolizumab, with no infectious or metabolic abnormalities, consistent with immune-mediated drug-induced liver injury. This case underscores the importance of continuous liver function monitoring throughout immunotherapy, even after long-term exposure, to enable early recognition and management of delayed immune-related hepatotoxicity.