Association Between Hospital Size and Outcomes of ES-SCLC Treated with Chemo-ICI: A Real-World Database Study in Japan

Background: Chemotherapy combined with immune checkpoint inhibitors is the standard first-line treatment for extensive-stage small-cell lung cancer. We evaluated whether hospital size, as a surrogate for institutional healthcare resources, was associated with treatment outcomes. Methods: This retrospective observational study used a nationwide electronic medical records database in Japan. Patients with extensive-stage small-cell lung cancer (ES-SCLC) receiving first-line platinum–etoposide plus atezolizumab or durvalumab between 2019 and 2022 were included. Patients were classified by hospital size (<500 vs. ≥500 beds) and compared after propensity score matching. The primary endpoint was time to treatment failure (TTF), and secondary endpoints included grade ≥ 3 hematological toxicities and hepatic impairments. Results: After matching, each group included 81 patients. Median TTF was 4.8 months in the <500-bed group and 4.9 months in the ≥500-bed group. In crude analyses, severe leukopenia occurred in 67.9% of patients in smaller hospitals and 45.7% in larger hospitals (RR, 0.67; 95% CI, 0.51–0.89; p = 0.007), whereas severe neutropenia occurred in 79.0% and 58.0% of patients, respectively (RR, 0.73; 95% CI, 0.59–0.91; p = 0.006). In sensitivity analyses accounting for hospital-level clustering, the association for leukopenia was maintained, whereas that for neutropenia was no longer statistically significant. Conclusions: No clear difference in TTF was observed between the hospital-size groups. Exploratory safety analyses showed differences in severe hematological toxicities, although the findings were not fully consistent after accounting for hospital-level clustering. Further studies are needed to clarify the relationship between institutional healthcare resources and treatment outcomes.