Identification of NK cell to predict prognosis in extensive-stage small cell lung cancer patients treated with immunotherapy plus chemotherapy

Background: Although the combination of immunotherapy and chemotherapy has emerged as a new standard for the first-line treatment of extensive-stage small cell lung cancer (ES-SCLC), there remains a dearth of prognostic markers of this novel therapeutic approach. In this study, we aimed to evaluate the efficacy of immunotherapy plus chemotherapy in patients with ES-SCLC and explore the potential prognostic markers. Methods: Pathologically confirmed ES-SCLC patients receiving immunotherapy plus chemotherapy as the first-line treatment were enrolled between July 2020 and August 2022 in this retrospective study. The natural killer (NK) cells in peripheral blood was collected at sequential time points. Kaplan-Meier method and log-rank test were utilized to calculate progression-free survival (PFS) and overall survival (OS). The prognostic value of the percentage of NK cells was evaluated by Cox proportional hazards regression analyses. Results: A total of 33 patients with ES-SCLC treated with immunotherapy plus platinum-etoposide were included for the analysis. At the time of data cutoff, the median PFS was 5.6 months and the median OS was 13.9 months. It was found that the percentage of NK cells at baseline was an independent factor of PFS(HR 0.142; 95% CI, 0.053–0.377; P＜0.001), and the difference between NK cell percentage at the time of optimal efficacy and baseline was an independent predictor factor of OS(HR 0.375; 95% CI, 0.169–0.832; P = 0.016). Conclusions: The study demonstrated that NK cells in peripheral blood could be used as a novel and convenient biomarker to predict the prognosis of patients with ES-SCLC treated with immunotherapy plus chemotherapy,which has significant implications for informing treatment decisions.