Delayed immune-related neutropenia with hepatitis by pembrolizumab

Lay abstract This case report describes a 72-year-old man with non-small-cell lung cancer who received four cycles of pembrolizumab-containing chemotherapy. He developed multiple immune-related adverse events (irAEs), which are significant side effects of immune checkpoint inhibitors (ICIs). Despite the discontinuation of pembrolizumab due to multiple irAEs, he developed immune-related hepatitis and neutropenia at 92 days and 118 days, respectively, after the final pembrolizumab dose. He received supportive care and immunosuppressive therapy and recovered from neutropenia. Recently, delayed development of irAEs was reported even in patients that discontinued ICIs; this is referred to as a delayed immune-related event (DIRE). This case developed strikingly delayed immune-related neutropenia as a DIRE. Clinicians should pay close attention to neutropenia as a possible life-threatening DIRE after ICI treatment.