8103 Background: Chemoimmunotherapy became the standard of care for extensive-stage small cell lung cancer (ES-SCLC) after two Phase III trials (IMpower133, CASPIAN) demonstrated significant improvement in overall survival (OS) over platinum-based chemotherapy. While both anti-PD-L1 agents provide durable responses in a subset (~10%), the magnitude of benefit with immunotherapy (IO) is similar, suggestive of therapeutic interchangeability. Real-world data (RWD) suggests durvalumab confers superior outcomes in ES-SCLC, compared to atezolizumab. Recently, durvalumab received regulatory approval for limited-stage SCLC, whereas atezolizumab failed to demonstrate benefit after chemoradiation. Here, we investigate whether IO choice impacts outcomes for first-line ES-SCLC. Methods: We retrospectively reviewed the charts of patients diagnosed with ES-SCLC in the Indiana University (IU) Health System from 2018 to 2024. Patients were stratified by receipt of either atezolizumab or durvalumab for first-line chemoIO for comparison of demographics and outcomes. Kaplan-Meier, univariate Cox regression, and Fishers exact test was applied. Results: We identified 158 patients diagnosed with ES-SCLC who received chemoIO (Table 1). Platinum-sensitivity and objective response rates were similar between groups ( P = 0.14 and P >0.9, respectively). The median number of IO cycles received (induction and maintenance) was significant higher with atezolizumab (9), compared to durvalumab (7, P 0.9 Sex (female) 79 (62%) 17 (55%) 96 (61%) 0.5 ECOG PS (0-1) 87 (74%) 20 (69%) 107 (73%) 0.6
Alfonso et al. (Thu,) studied this question.