Early Tumor Shrinkage as a Predictor of Favorable Treatment Outcomes in Patients With Extensive-Stage SCLC Who Received Programmed Cell Death-Ligand 1 Inhibitor Plus Platinum-Etoposide Chemotherapy: A Prospective Observational Study

Introduction: In recent years, programmed cell death-ligand 1 (PD-L1) inhibitor plus platinum-etoposide chemotherapy was found to have favorable clinical outcomes in patients with extensive-stage SCLC (ES-SCLC). The usefulness of early tumor shrinkage (ETS) has been reported in various types of cancers. Nevertheless, 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. 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. Results: The responders (progression-free survival [PFS] ≥ 6.0 mo) had significantly greater tumor shrinkage at the first evaluation than the nonresponders (PFS < 6.0 mo) (65.0% versus 53.7%, p = 0.03). We defined the cutoff value for ETS as a 57% change from the baseline on the basis of 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 than those who did not achieve ETS (5.6 versus 4.0 mo, log-rank test p = 0.001 and 15.0 versus 8.3 mo, log-rank test p = 0.02). In the multivariate analyses, ETS was significantly associated with PFS and overall survival (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). Conclusions: 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

Analysis of Tumor Heterogeneity Through AXL Activation in Primary Resistance to EGFR Tyrosine Kinase Inhibitors

Introduction: EGFR tyrosine kinase inhibitors are standard therapeutic agents for patients with advanced NSCLC harboring EGFR mutations. Nevertheless, some patients exhibit primary resistance to EGFR tyrosine kinase inhibitors in the first-line treatment setting. AXL, a member of the TYRO3, AXL, and MERTK family of receptor tyrosine kinases, is involved in primary resistance to EGFR tyrosine kinase inhibitors in EGFR-mutated NSCLC. Methods: We investigated spatial tumor heterogeneity using autopsy specimens and a patient-derived cell line from a patient with EGFR-mutated NSCLC having primary resistance to erlotinib plus ramucirumab. Results: Quantitative polymerase chain reaction analysis revealed that AXL mRNA expression differed at each metastatic site. In addition, AXL expression levels were likely to be negatively correlated with the effectiveness of erlotinib plus ramucirumab therapy. Analysis of a patient-derived cell line established from the left pleural effusion before initiation of treatment revealed that the combination of EGFR tyrosine kinase inhibitors and an AXL inhibitor remarkably inhibited cell viability and increased cell apoptosis in comparison with EGFR tyrosine kinase inhibitor monotherapy or combination therapy of these inhibitors with ramucirumab. Conclusions: Our observations suggest that AXL expression may play a critical role in the progression of spatial tumor heterogeneity and primary resistance to EGFR tyrosine kinase inhibitors in patients with EGFR-mutated NSCLC