Peripheral Lymphocyte Count as a Surrogate Marker of Immune Checkpoint Inhibitor Therapy Outcomes in Patients with Non-Small-Cell Lung Cancer

Abstract BackgroundDegree of expression of programmed death-ligand 1 (PD-L1) is related with Immune check point inhibitors (ICIs) response but is not obligate predictive marker and needs sufficient tissue. Therefore, there is unmet need for easily accessible peripheral blood (PB) biomarkers and evaluation of the prognostic value of this marker is needed. We investigated the application of serum peripheral lymphocyte count (PLC) as a predictive PB biomarker for ICI response in patients with NSCLC. MethodsWe conducted a retrospective study and reviewed the medical charts of patients with NSCLC who were treated with ICIs at Seoul National University Hospital. We evaluated the association between PLC and progression-free survival using a Cox proportional hazard model. The PLC before and after 1 month of immunotherapy was collected. The quartile groups of PLC were compared using the Kruskal-Wallis statistical test.ResultsA total of 231 patients were treated with immunotherapy for NSCLC. The median follow-up period was 4.7 months. During the follow-up period, the disease progressed in 138 patients (59.7%). The post-treatment PLC groups Q2-4 showed significantly lower disease progression than group Q1 in our adjusted model (Q4 hazard ratio: 0.41, 95% confidence interval: 0.25–0.68, p < 0.001). The overall survival also showed similar results. An association between adverse events and PLC was not observed in this study. ConclusionWe revealed that an increased post-treatment PLC was associated with favorable progression-free and overall survival with NSCLC patients treated with ICIs. Therefore, PLC could be a surrogate marker for ICI responses in NSCLC.