Cost-effectiveness study of atezolizumab (ATZ) vs. durvalumab (DUR): Real-world data (RWD) on first-line chemotherapy combined with immune-checkpoint inhibitors (Chemo-ICIs) for extensive disease small-cell lung cancer (ED-SCLC).

8097 Background: Chemo-ICI is the standard of care in first-line therapy for ED-SCLC. Although there is no comparative data on ATZ vs. DUR, their efficacies appear to be equivalent based on results from IMpower133 and CASPIAN trials. On the other hand, the drug price of DUR is higher than that of ATZ, suggesting a different cost-effectiveness. Methods: This is a multicenter retrospective study of RWD. Clinical outcomes and safety information of ED-SCLC patients (pts) who had received Chemo-ICIs were collected from electronic medical records, and the total cost incurred during ICIs was obtained from the receipts of each hospital. Propensity score matching (PSM) was performed to adjust difference of pts' backgrounds of two groups (ATZ-G vs. DUR-G). The total monthly medical costs incurred during ICI administration for both groups were compared by cost minimization analysis to evaluate cost-effectiveness. Results: From August 2018 to December 2022, 274 pts (ATZ/DUR: 176/98) were extracted from 8 hospitals in Japan. After PSM and exclusion of cisplatin-treated pts, total 128 pts: 64 pts in each group were evaluated. The mean total medical costs per month during ICIs were 1,003,922 (±310,192) JPY (6,783 USD) in the ATZ-G and 1,596,511 (±371,405) JPY (10,787 USD) in the DUR-G (Wilcoxon rank sum test: p < 0.001). Mean ICI drug costs per month during ICIs were 799,079 (±89,555) JPY (5,399 USD) in the ATZ-G and 1,570,744 (±371,405) JPY (10,163 USD) in the DUR-G (p < 0.001). Response rate was 73.4% for ATZ-G and 75.0% for DUR-G. Median overall survivals (OSs) of ATZ-G vs. DUR-G were 13.9 (95% confidence interval [CI]: 11.7-17.5) vs. 13.6 (95% CI: 11.0-20.0) months, respectively (p = 0.919). Median progression-free survivals of ATZ-G vs. DUR-G were 4.9 (95% CI: 4.4-5.6) vs. 5.6 (95% CI: 5.0-6.7) months, respectively (p = 0.060). Cox-proportional hazard model identified poor performance status (hazard ratio [HR]: 5.5, p < 0.001) and bone metastases (HR: 1.8, p = 0.029) as significant factors for shorter OS, while ATZ vs. DUR was not significant. ATZ-G revealed lower incidences of immune-related adverse events (irAEs) ≥grade 2 (10.9 vs. 31.3%, p = 0.009) and any grade interstitial lung disease (ILD) (3.1 vs. 20.3%, p = 0.004) than DUR-G. Number of hospitalizations in ATZ-G (median 1, range 0-6) was lower than that in DUR-G (median 2, range 0-7) (p = 0.005). Conclusions: Our RWD demonstrated a superior cost-effectiveness of ATZ to that of DUR. Total efficacies were similar, whereas the safety profiles, including irAE and ILD were more favorable in ATZ-G. Further discussion is required regarding not only cost-effectiveness but also clinical practicality such as: dose schedule of 3 weeks vs. 4 weeks; regimen flexibility of carboplatin vs. cisplatin; and etoposide dose adjustment of 100 mg/m 2 vs. 80 mg/m 2 . Clinical trial information: 000053483.