Diagnostic guide for immune checkpoint inhibitor-induced liver injury

With the widespread use of immune checkpoint inhibitors (ICIs), liver injury (ICI-induced liver injury) as an immune-related adverse event has become a major concern in clinical practice. Because severe cases of liver injury require administration of corticosteroids, a comprehensive evaluation is crucial, including clinical course, blood and imaging tests, and if necessary, pathological examination through liver biopsy. As with liver injury induced by other drugs, classification of injury type by R-value is useful in deciding treatment strategies for ICI-induced liver injury. Histologically, the most representative feature is an acute hepatitis-like hepatocellular injury, characterized by diffuse lobular inflammation accompanied by CD8-positive T lymphocytes. Another condition that can cause liver injury during ICI treatment is cholangitis accompanied by non-obstructive bile duct dilatation and bile duct wall thickening. Many cases of ICI-induced cholangitis are classified as non-hepatocellular injury type, and they have been reported to respond poorly to corticosteroids. It is essential that gastroenterologists/hepatologists and doctors in various departments work in cooperation to develop a system that achieves early diagnosis and appropriate treatment of ICI-induced liver injury.