Abstract
BACKGROUND: Immunotherapy with atezolizumab and durvalumab has significantly advanced the treatment of extended-stage small cell lung cancer (esSCLC). We aimed at studying the real-world use and comparative effectiveness and safety of these treatments. METHODS: We utilised the French National Health Data System (SNDS) to include all patients treated with atezolizumab or durvalumab for esSCLC from May 1, 2019 to December 31, 2023, with follow-up until June 30, 2024. Baseline characteristics were described. Effectiveness (time to treatment discontinuation and overall survival) and safety (all-cause and cause-specific overnight hospitalisations) were assessed using Cox proportional hazards models. FINDINGS: A total of 8612 patients were included, with 5188 initiating atezolizumab and 3424 initiating durvalumab. The mean age at inclusion was 66·2 years (standard deviation 8·7), and most patients were men (63·8%, n = 5493). The median time to treatment discontinuation was 5·4 months (95% CI, 5·3-5·5) for atezolizumab and 5·5 months (95% CI, 5·4-5·6) for durvalumab, with an adjusted hazard ratio (aHR) of 0·97 (95% CI, 0·92-1·02) for durvalumab vs. atezolizumab. The median overall survival was 11·1 months (95% CI, 10·6-11·4) for atezolizumab and 11·4 months (95% CI, 10·9-11·9) for durvalumab, with an aHR of 0·93 (95% CI, 0·88-0·98) for durvalumab vs. atezolizumab.While 61·8% (n = 5323) of patients received systemic steroids, testifying of immune-mediated side effects, no significant safety differences were observed between the groups. INTERPRETATION: Our study found no clinically relevant differences in effectiveness or safety between atezolizumab and durvalumab for first-line esSCLC. Both treatments appearing interchangeable, treatment decision could be based on drug availability, local institutional protocols, administrative organisation, or cost considerations. FUNDING: None.