[Aplastic anemia developed after treatment with durvalumab]

A 76-year-old woman with stage IIIB squamous cell lung carcinoma developed pancytopenia following maintenance therapy with durvalumab. She was diagnosed with squamous cell lung carcinoma (T4N2M0, stageIIIB) in December 2023. Following a favorable response to chemoradiotherapy, maintenance therapy with durvalumab was initiated in June 2024. Thrombocytopenia was observed starting in August, and platelet count had decreased to 22,000/µl in October, leading to the discontinuation of durvalumab. However, the condition progressed to pancytopenia. Bone marrow biopsy revealed hypocellular marrow without dysplasia, fibrosis, or hemophagocytosis. Additional findings included paroxysmal nocturnal hemoglobinuria-type blood cells and fatty marrow replacement on spinal MRI. Based on these comprehensive findings, the patient was diagnosed with aplastic anemia (AA) in January 2025. Immunosuppressive therapy combining antithymocyte globulin, cyclosporine A, and eltrombopag was initiated in February 2025, resulting in a favorable response. AA is a relatively rare immune-related adverse event, and reports of AA induced by durvalumab are extremely limited. This case highlights the importance of considering AA in the differential diagnosis of persistent thrombocytopenia or pancytopenia during immune checkpoint inhibitor therapy.