Case Report: Fatal osimertinib-related interstitial lung disease during adjuvant therapy after left pneumonectomy in a patient with lung adenocarcinoma undergoing maintenance hemodialysis.

Osimertinib is recommended not only for advanced EGFR-mutated non-small cell lung cancer (NSCLC) but also as adjuvant therapy after complete resection, leading to increasing opportunities for its clinical use. However, interstitial lung disease (ILD) is a serious adverse event, and its incidence and severity have been reported to be higher in Japanese patients. We report a fatal case of osimertinib-related ILD that developed during adjuvant therapy in a patient undergoing maintenance hemodialysis after left pneumonectomy. A 71-year-old man was found to have a left upper lobe mass on chest computed tomography (CT) performed at the initiation of maintenance hemodialysis for nephrosclerosis. Transbronchial biopsy was nondiagnostic; however, lung cancer was strongly suspected clinically, and video-assisted thoracoscopic left pneumonectomy with mediastinal lymph node dissection was performed. Pathological examination revealed lung adenocarcinoma harboring an EGFR exon 19 deletion, pT2aN2bM0 (stage IIIB). Adjuvant osimertinib (80 mg/day) was initiated. Exertional dyspnea developed 37 days after treatment initiation, and chest CT on day 40 revealed peripheral ground-glass opacities in the remaining right lung. Osimertinib was discontinued, and empirical antibiotic therapy was initiated because both osimertinib-related ILD and infection were considered in the differential diagnosis. Shortly after admission, the patient developed rapidly progressive respiratory failure. Although steroid pulse therapy led to temporary improvement, the respiratory status deteriorated again, and the patient died on day 57 after osimertinib initiation despite an additional course of steroid pulse therapy. This case highlights that osimertinib-related ILD can become fatal not only in advanced or recurrent disease but also during curative-intent adjuvant therapy. Careful monitoring and prompt evaluation and intervention are particularly important in patients with poor respiratory reserve.