Bridging Knowledge Gaps in Small Cell Lung Cancer: Data, Challenges and Priorities.

Small Cell Lung Cancer (SCLC) is an aggressive neuroendocrine malignancy representing approximately 15% of all lung cancers. Characterized by rapid progression, early metastasis, and high circulating tumor cell burden, SCLC has a poor prognosis. Although initial responses to chemotherapy, radiotherapy, and immunotherapy are common, relapse due to acquired resistance is nearly inevitable. Molecular studies have identified four transcription factor-driven subtypes-ASCL1, NEUROD1, POU2F3, and YAP1-each with distinct biological traits and therapeutic vulnerabilities. However, clinical classification remains largely homogeneous, limiting precision treatment strategies. Immunotherapy has modestly improved survival, as demonstrated in trials like IMpower133, CASPIAN, and ADRIATIC. Yet only a small subset of patients-approximately 12%-achieve long-term survival beyond five years. Understanding the biological and immunological profiles of these exceptional responders is critical. Future research should prioritize comprehensive biomarker integration, including PD-L1, TMB, DLL3, CD3, and emerging targets. Novel agents such as tarlatamab (DLL3-targeting) and ifinatamab deruxtecan (B7-H3-targeting) have shown encouraging efficacy in early-phase trials, though predictive markers remain elusive. A multi-dimensional approach combining tissue, blood, and immune profiling is essential to advance precision oncology in SCLC and improve patient selection for emerging therapies.