Tarlatamab in Relapsed SCLC With Idiopathic Pulmonary Fibrosis: A Case With Comparative DLL3 Expression Analysis: Case Report.

There is no established treatment for relapsed SCLC in patients with interstitial lung disease. We report the case of a 67-year-old man with idiopathic pulmonary fibrosis (IPF) receiving nintedanib who developed a postoperative relapse of SCLC. After cisplatin plus etoposide therapy, the patient developed an acute exacerbation of IPF, which improved with corticosteroid therapy. However, pleural dissemination and pulmonary metastases progressed, leading to the initiation of tarlatamab. During follow-up, transient ground-glass opacities appeared around pulmonary metastases. These opacities resolved, and tumor shrinkage was observed. The patient achieved a partial response without new toxicities, and the therapy was ongoing. Immunohistochemical analysis using an anti-delta-like ligand 3 antibody (SP347) reported strong expression in tumor cells but no detectable expression in adjacent normal or fibrotic lung tissue. This finding provides a possible biological rationale. This case suggests that tarlatamab may be a potential therapeutic option in selected patients with relapsed SCLC complicated by IPF.