Continuation of Tarlatamab With Concomitant Radiotherapy for Oligoprogression in Extensive-Stage Small-Cell Lung Cancer: A Report of Two Cases.

Tarlatamab, a bispecific T-cell engager immunotherapy targeting CD3 on T cells and delta-like ligand 3 on tumor cells, has demonstrated promising efficacy in patients with relapsed extensive-stage small-cell lung cancer (ES-SCLC). However, therapeutic strategies for oligoprogressive disease during tarlatamab treatment remain unestablished. We report two patients with ES-SCLC who continued tarlatamab treatment following radiotherapy for oligoprogressive disease. In Case 1, a 63-year-old man receiving fifth-line tarlatamab developed a solitary brain metastasis despite sustained extracranial disease control. Stereotactic radiotherapy achieved marked regression of the lesion, allowing continuation of tarlatamab treatment. In Case 2, a 78-year-old man receiving fourth-line tarlatamab developed isolated progression of a subcarinal lymph node metastasis after an initial partial response. Hyperfractionated radiotherapy resulted in rapid normalization of tumor marker levels and marked nodal shrinkage, enabling ongoing tarlatamab treatment. These cases suggest that radiotherapy to the progressing site may effectively control oligoprogression during tarlatamab treatment, permitting continuation of systemic therapy in selected patients with ES-SCLC. This approach may represent a useful treatment strategy for managing oligoprogressive disease during tarlatamab therapy.