Combined chemoradiotherapy and programmed cell death-ligand 1 blockade leads to changes in the circulating T-cell receptor repertoire of patients with non-small-cell lung cancer.

Combined chemoradiotherapy (CRT) and programmed cell death-ligand 1 (PD-L1) blockade is a new care standard for unresectable stage III non-small-cell lung cancer (NSCLC). Although this consolidation therapy has improved the overall survival of patients with NSCLC, the synergistic action mechanisms of CRT and immunotherapy on T cells remain unclear. In addition, there is a paucity of reliable biomarkers to predict clinical responses to therapy. In this study, we analyzed T-cell receptor (TCR) sequences in the peripheral blood of five patients with NSCLC. T-cell receptor analysis was undertaken before treatment, after CRT, and after PD-L1 blockade. Notably, we observed the expansion and alteration of the dominant T-cell clonotypes in all cases with a complete response. In contrast, neither expansion nor alteration of the TCR repertoire was observed in cases with progressive disease. T cell expansion was initiated after CRT and was further enhanced after PD-L1 blockade. Our findings suggest the systemic effect of CRT on circulating T cells in addition to the curative effect on limited tumor sites. Dynamic changes in circulating T-cell clonotypes could have a prognostic significance for combined CRT and PD-L1 blockade.