A case of organizing pneumonia in rearranged during transfection fusion-positive lung adenocarcinoma treated with selpercatinib.

Selpercatinib is the first targeted therapy for rearranged during transfection (RET) fusion-positive unresectable non-small-cell lung cancer (NSCLC). The main adverse effects of selpercatinib include hypertension, liver dysfunction, diarrhea, and QT prolongation on electrocardiograms. However, instances of drug-induced interstitial lung disease (DI-ILD) are infrequently reported. We describe the first case of a patient with RET fusion-positive NSCLC treated with selpercatinib who developed DI-ILD, confirmed pathologically. The patient, a 72-year-old woman, initiated selpercatinib treatment following the postoperative recurrence of lung adenocarcinoma. After 15 months of treatment, computed tomography scans revealed multiple infiltrates and ground-glass opacities in both lungs. A thoracoscopic lung biopsy identified organizing pneumonia, attributed to DI-ILD caused by selpercatinib. Although she was asymptomatic, the patient's selpercatinib treatment was discontinued, leading to a gradual improvement in the lung infiltrates. Despite the lack of detailed reports, DI-ILD with selpercatinib represents a potentially serious adverse event and should be approached with caution.