Real-world insights into advanced combined small cell lung cancer: Clinical characteristics and therapy.

e20112 Background: Combined small cell lung cancer (C-SCLC) represents a rare subset of small cell lung cancer, with limited clinical data available, particularly in the context of the immunotherapy era. This study aims to delineate the clinicopathological features and explore the prognosis of C-SCLC patients following systematic anti-tumor treatment. Methods: BetweenJanuary 2017 and December 2023, lung cancer patients who presented at Sir Run Run Hospital were reviewed, and clinical data of pathologically confirmed advanced C-SCLC patients who received systematic therapy were collected retrospectively, including demographic and pathological characteristics, treatment, and efficacy. This analysis aims to evaluate the tumor response and progression-free survival (PFS) to investigate the systematic therapeutic modalities and prognosis of C-SCLC patients within real-world clinical practice. Results: This study involved 30 initially diagnosed C-SCLC patients who received systematic anti-tumor therapy. Of those, 83.3% (n=25) were males, with a mean age of 63.8 years, and 66.7% (n=20) were non-smokers. All patients had an ECOG score of 1, and 18 (60.0%) reported distant organ metastases. For the mixed tumor histology, squamous cell carcinoma (n=11, 36.7%) and adenocarcinoma (n=11, 36.7%) were the most frequently observed components. Immunochemotherapy was delivered to 13 (43.3%) patients, the majority of whom were treated with the anti-PD-1 inhibitor serplulimab (6/13, 46.2%); 11 (36.7%) were treated with platinum-based chemotherapy alone; 6 (20.0%) underwent anti-EGFR- or anti-VEGF-based therapy. Among 27 patients with measurable disease, 23 patients achieved disease control, resulting in an objective response rate (ORR) of 51.9% (14/27; 95% CI: 32.0% - 71.3%) and disease control rate (DCR) of 85.2% (23/27; 95% CI: 66.3% - 95.8%). Two patients had target lesions disappear after receiving serplulimab-based immunochemotherapy, one mixed with squamous cell carcinoma and the other mixed with large cell carcinoma. The median follow-up duration was 9.7 months. Overall, 18 patients (60.0%) had reported PFS events, with the median PFS being 9.7 months (95% CI: 4.4 – 18.7) and the 6-month PFS rate being 57.3% (95% CI: 40.7% - 80.6%). The median PFS of C-SCLC patients mixed with adenocarcinoma (9.7 months; 95% CI: 4.4 – not reached) was numerically higher than those mixed with squamous cell carcinoma (4.2 months; 95% CI: 4.0 – not reached). Conclusions: Our findings may provide helpful stratifications for clinical decision-making of systematic treatment in C-SCLC patients. The prognosis of patients may be related to the mixed tumor cell, and further follow-up is required.