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

Abstract 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.