Abstract
PURPOSE: Identifying patients at high risk of immune-related adverse events (irAEs) that impede the achievement of durable efficacy of programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) blockade therapy is important in improving their management. Identification of a novel predictive factor of therapeutic benefit is also important in improving patient selection for treatment with PD-1/PD-L1 inhibitors. Further determinants driving response and linking with irAEs are urgently required. METHODS: To address these unmet needs in the field, we explored whether 27 soluble checkpoint proteins and immunomodulatory proteins in serum at the therapy baseline and after week 3 were associated with irAE onset and therapeutic efficacy using MILLIPLEX Human Immuno-Oncology Checkpoint Protein Panel assays in a prospective, multicenter cohort of 81 patients with non-small cell lung cancer (NSCLC) receiving atezolizumab monotherapy. RESULTS: By competing-risks regression analysis, we identified that high levels of B cell-activating factor (BAFF) at baseline were a significant and strong risk factor of irAEs (hazard ratio, 5.61; 95% confidence interval, 2.43-12.96; P < 0.0001). We also identified that increased inducible T cell co-stimulator (ICOS) during the first therapeutic cycle was an independent factor associated with prolonged progression-free survival and overall survival. CONCLUSION: These findings are in keeping with the reported mechanistic basis of these molecules and may provide potential guidance for clinical decision-making to improve patient care. Further validation studies are warranted. Trial registration UMIN000035616 (January 28, 2019).