Atezolizumab vs durvalumab for extensive-stage small cell lung cancer in Japan: a real-world comparative analysis of costs and clinical outcomes.

BACKGROUND: Platinum-etoposide combined with a PD-L1 inhibitor (atezolizumab or durvalumab) is the standard first-line treatment for extensive-stage small cell lung cancer (ES-SCLC). Although phase 3 trials have demonstrated similar efficacy, no direct comparison exists, and differences in treatment cost and resource utilization may influence clinical decision-making. METHODS: In this multicenter retrospective study, real-world data from eight Japanese institutions were analyzed. Patients with ES-SCLC treated with platinum-etoposide plus atezolizumab or durvalumab between August 2018 and December 2022 were included. Individual-level medical costs were calculated from health insurance claims linked to electronic medical records. After propensity score matching and exclusion of cisplatin-treated patients, 128 patients were analyzed. The primary outcome was mean monthly medical cost during immunotherapy. Secondary outcomes included overall survival (OS), immune-related adverse events (irAEs), and prognostic factors. RESULTS: Among 128 patients (mean age, 74 years; 85% male), mean monthly medical cost was significantly lower with atezolizumab than durvalumab (¥1 003 922 [$7183] vs ¥1 596 511 [$11 422]; P < .001). Median OS was comparable (13.9 months [95% CI, 11.7-17.5] vs 14.8 months [95% CI, 10.5-not reached]; P = .92). Grade ≥2 irAEs (11% vs 31%; P = .009) and interstitial lung disease (3% vs 20%; P = .004) were less frequent with atezolizumab. Poor performance status was associated with worse OS, whereas treatment type was not. CONCLUSIONS: Atezolizumab was associated with lower medical costs and similar survival outcomes compared with durvalumab in ES-SCLC, suggesting its use as a clinically comparable option with lower associated costs in Japanese real-world practice.