438P Chemoimmunotherapy versus chemotherapy for extensive-stage small cell lung cancer: A retrospective real-world study of 904 patients

Background: Extensive-stage SCLC (ES-SCLC) progresses rapidly and is often diagnosed with brain, liver, or bone metastases upfront.While PD-L1 CPI such as atezolizumab (Atezo) or durvalumab (Durva) combined with platinum-etoposide prolonged survival in clinical trials, real-world effectiveness across ECOG PS 2, metastatic subgroups, and for inclusion of radiotherapy (RTx) is not sufficiently defined.This study evaluates population-based data from the Baden-Wrttemberg Cancer Registry (BWCR), Germany. Methods:We retrospectively analyzed ES-SCLC patients (pts) diagnosed 2018-2024 who received Carboplatin-etoposide (Carbo+Eto), Carbo+Eto+Atezo, Carbo+Eto+-Durva, or Cisplatin+Eto+Durva. ECOG PS (0-2), metastatic sites, and administration of thoracic or cranial RTx were recorded.Overall survival (OS) was assessed using Kaplan-Meier-and Cox-models.Results: Among 1,632 pts (median age 67; 58% male), 573 received Carbo+Eto, 831 Carbo+Eto+Atezo, 178 Carbo+Eto+Durva and 50 Cisplatin+Eto+Durva.Carbo+Eto showed the poorest OS, while Atezo-and Durva-based regimens demonstrated similar outcomes.In ECOG 0-1, ICI+chemotherapy significantly improved OS (median 10.64 vs. 8.56 months; p<0.0001), confirmed by multivariate analysis (HR 0.78; 95% CI 0.69-0.89).Thoracic RTx also improved OS (HR 0.70; 95% CI 0.50-0.83).In ECOG 2, ICI+chemotherapy conferred clear early benefit (median OS 7.14 vs. 5.52 months; 6month OS 60% vs. 47%; 12-month OS 29% vs. 20%), with non-proportional hazards due to later curve crossing.ICI significantly prolonged OS in pts with brain metastases (HR 0.70; 95% CI 0.55-0.89),who benefited from cranial but not thoracic RTx.Pts without brain metastases benefited from both thoracic RTx and PCI.No significant OS benefit from ICI was seen in pts with liver metastases, bone metastases, or 3 metastatic sites.Conclusions: PD-L1 CPI improve survival in real-world ES-SCLC pts across ECOG 0-2.Benefit is observed in pts with brain metastases but is not confirmed in liver, bone, or high metastatic burden situations.RTx remains an important strategy in multimodality management of ES-SCLC.