Research Article|Articles in Press, 100493

Early tumor shrinkage as a predictor of favorable treatment outcomes in patients with extensive stage-small cell lung cancer who received programmed cell death-ligand 1 inhibitor plus platinum-etoposide chemotherapy: A prospective observational study

Open AccessPublished:February 28, 2023DOI:
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      In recent years, programmed cell death-ligand 1 (PD-L1) inhibitor plus platinum-etoposide chemotherapy has shown favorable clinical outcomes in patients with extensive-stage small cell lung cancer (ES-SCLC). The usefulness of early tumor shrinkage (ETS) has been reported in various types of cancers. However, there have been few reports evaluating ETS in ES-SCLC. Therefore, this study aimed to evaluate the role of ETS in the clinical outcomes of patients with ES-SCLC receiving chemoimmunotherapy.

      Materials and Methods

      We prospectively identified 46 patients with ES-SCLC who received PD-L1 inhibitor plus platinum-etoposide chemotherapy at 10 institutions in Japan between September 2019 and October 2021. Of them, 35 patients were selected for analyses.


      The responders (progression-free survival [PFS] ≥ 6.0 months) had significantly greater tumor shrinkage at the first evaluation than the non-responders (PFS < 6.0 months) (65.0 vs. 53.7%, p = 0.03). We defined the cut-off value for ETS as a 57% change from the baseline based on the receiver operating characteristic results to determine the optimal tumor shrinkage rate at the first evaluation for identifying responders. The patients with ES-SCLC who achieved ETS had longer PFS and overall survival (OS) than those who did not achieve ETS (5.6 vs. 4.0 months, log-rank test p = 0.001 and 15.0 vs. 8.3 months, log-rank test p = 0.02). In the multivariate analyses, ETS was significantly associated with PFS and OS (hazard ratio, 0.27; 95% confidence interval, 0.12–0.63; p = 0.002 and hazard ratio, 0.34; 95% confidence interval, 0.13–0.85; p = 0.02).


      Our prospective observational study indicated that ETS was related to favorable clinical outcomes for patients with ES-SCLC receiving PD-L1 inhibitor plus platinum-etoposide chemotherapy.