A retrospective study of first line atezolizumab-carboplatin-etoposide in extensive-stage small cell lung cancer: Real world data from a Spanish tertiary center.

e20100 Background: The association of immune checkpoint inhibitors (ICIs) with Platinum-Etoposide (PE) has been established as the standard treatment in extensive stage Small Cell Lung Cancer (ES-SCLC). We present a real-world analysis, conducted in a Spanish tertiary hospital, that assesses the efficacy and safety of Atezolizumab combined to Carboplatin-Etoposide (Atezo-CE) in first-line ES-SCLC treatment, based on the Impower-133 Clinical Trial (CT). Methods: In this longitudinal, retrospective study, we analysed the patients (pts) diagnosed with ES-SCLC and treated at our center from July 2020 to June 2023, comparing outcomes of PE chemotherapy and Atezo-CE regime. Primary endpoints were overall survival (OS), progression-free survival (PFS) and safety. We contrasted our findings to those obtained in trials that used different ICIs: Impower-133 (Atezolizumab), CASPIAN (Durvalumab) or KEYNOTE-604 (Pembrolizumab). Data analysis employed Chi-square, Kaplan-Meier and Log-Rank. Results: Over 35 months (m), 41 pts with ES-SCLC were treated in our center: 19 pts received PE (57.9% Cisplatin and 42.1% Carboplatin), and 22 received Atezo-CE. In the PE group: 42.1% completed 6 cycles, 21.1% 4 cycles, and 36.8% less than 4. In the Atezo-CE cohort: 81.8% completed 4 cycles, and 18.2% less than 4. Regarding Performance Status (PS) in the PE cohort vs the Atezo-PE group: PS 0 0 vs 4.5%; PS 1 47.4 vs 77.3%; PS 2 42.1 vs 18.2%; PS 3 10.5 vs 0%. Corticosteroid therapy was ongoing in 52.6% vs 50% of PE vs Atezo-CE pts, respectively, adding the ICI in later cycles without affecting total cycles of Atezo received (6.8 in our study vs 7 in the Impower-133). Adverse effects (AEs) occurred in 73.7% of PE pts vs 100% of Atezo-CE pts (68.2% chemo-induced and 31.8% immune-related). Common AEs in both groups were anemia, thrombopenia, leukopenia, asthenia and vomiting. Skin and thyroid AEs were the most frequent ICI-related. Chemotherapy dose reduction occurred in 47.4% vs 27.3% and suspension in 5.3% vs 13.3% of PE pts vs Atezo-CE pts, respectively. OS was higher in the Atezo-CE group, 11.7m (95% CI: 9.2-14.2m) compared to 6.8m (95% CI: 3.8-9.8m) in the PE cohort, p-value 0.008. PFS also favoured Atezo-CE pts, 6.9m (95% CI: 5-8.7m) vs 5m (95% CI: 2.8-7.2m) in the PE cohort, though not statistically significant, p-value 0.249. Compared to the CTs Impower-133, CASPIAN and KEYNOTE-604, which reported OS of 12.3m, 12.9m and 10.8m, respectively, and PFS of 5.2m (Impower-133) and 4.2m (KEYNOTE-604), our study with pts with worse PS and needing corticosteroids at treatment initiation (exclusion criteria in CTs), showed comparable outcomes. Conclusions: Our study underscores the importance of adding ICIs to ES-SCLC first-line treatment. It further emphasizes the need for a deeper knowledge in molecular profiling and biomarker-driven strategies to tailor ES-SCLC therapy more effectively.