Pembrolizumab‐Induced Severe Pneumonitis in a Patient With Lung Adenocarcinoma After Umbilical Cord Blood Transplantation: A Case Report

Immune checkpoint inhibitors (ICIs) are essential treatments for lung cancer, but their safety following allogeneic haematopoietic stem cell transplantation (allo-HSCT) remains unclear. We report a case of a 66-year-old man who underwent umbilical cord blood transplantation for acute lymphoblastic leukaemia and later developed lung adenocarcinoma. Pembrolizumab monotherapy was initiated, but the patient developed severe steroid-refractory immune-related pneumonitis, leading to mortality 56 days after treatment initiation. Given the scarcity of reports on ICI use in lung cancer patients with prior HSCT, this case highlights critical safety considerations.