Molecular Subtyping of Extensive Stage Small Cell Lung Cancer and Relevent Clinical Significance

This retrospective observational study examines the predictive value of transcriptome-based molecular subtyping of extensive stage SCLC for PD-1/PD-L1 inhibitor efficacy and explores immune microenvironment differences between subtypes to uncover immunotherapy resistance mechanisms. Patients with extensive stage SCLC receiving first-line standard treatment are enrolled, and baseline tumor tissue and peripheral blood samples are collected for transcriptome sequencing and immunohistochemistry (IHC). Based on results, patients are classified into four molecular subtypes, and treatment efficacy and safety are recorded. The study compares the efficacy between SCLC subtypes to determine if molecular typing predicts immunotherapy efficacy and investigates immune microenvironment differences between subtypes to uncover resistance mechanisms. Treatment regimens follow first-line extensive stage SCLC guidelines, including cisplatin+etoposide or carboplatin+etoposide and PD-(L)1 inhibitors, with options determined by the supervising physician.