Tracking Peripheral Memory T Cell Subsets in Advanced Nonsmall Cell Lung Cancer Treated with Hypofractionated Radiotherapy and PD-1 Blockade.

Hypofractionated radiotherapy (HFRT) or chemotherapy combined with programmed death-1 (PD-1) blockade has achieved good clinical control in advanced nonsmall cell lung cancer (NSCLC). However, the relative influence of HFRT + PD-1 blockade and chemo-immunotherapy on peripheral memory T cell subsets in NSCLC responders has not been evaluated in clinical practice. Thirty-nine patients with advanced NSCLC were enrolled. The frequencies of naive (Tn; CD45RA(+)CCR7(+)), central memory (Tcm; CD45RA(-)CCR7(+)), effector memory (Tem; CD45RA(-)CCR7(-)), and effector memory RA (TemRA; CD45RA(+)CCR7(-)) T cell subsets and PD-1 expression were analyzed in CD4(+) and CD8(+) T cells using flow cytometry from peripheral blood samples. The correlations of memory T cell subsets and PD-1 expression with overall survival in HFRT + PD-1 blockade group were examined using the Kaplan-Meier method. Patients with partial response to HFRT + PD-1 blockade showed reduction in Tn and expansion in TemRA cell subpopulations among CD8(+) T cells and reduced PD-1(+)CD4(+) and PD-1(+)CD8(+) T cells, all of which were significantly correlated with overall survival. The responders to chemo-immunotherapy showed expansion of the TemRA and decrease of Tcm in CD8(+) T cell subpopulation. Our findings show that HFRT+PD-1 blockade and chemo-immunotherapy combination therapies induce differential memory T cell subset differentiation, offering predictive markers for treatment response. Clinical Trial Information: https://clinicaltrials.gov/ct2/show/ChiCTR-1900027768.