Sequential Immune Activation of Effector T Cells as Biomarkers of Response to Durvalumab in Patients with Locally Advanced NSCLC

Purpose: Durvalumab therapy following concurrent chemoradiotherapy (cCRT) improves progression-free survival (PFS) in patients with unresectable locally advanced non–small cell lung cancer. In this prospective observational study, we evaluated the changes in peripheral blood immune cell counts to elucidate the immunologic mechanisms underlying cCRT and durvalumab therapy.
Experimental Design: Peripheral blood mononuclear cell (PBMC) samples were collected at four time points: before cCRT, after cCRT, at the start of durvalumab, and 8 weeks after the start of durvalumab, and analyzed by multicolor flow cytometry.
Results: Of the 149 enrolled patients, 115 received durvalumab consolidation therapy after cCRT. The median PFS in the overall population was 24.2 months, and the 3-year PFS rate was 38.9%. PBMC analysis showed an increased effector fraction of CD4+ T cells before and after cCRT but no change in CD8+ T cells. Following durvalumab therapy, the effector fraction ratio of CD8+ T cells (CD62Llow CD8+ T cells) increased and positively correlated with increased CD62Llow CD4+ T cells during cCRT. Patients whose proportion of CD62Llow CD4+ T cells exceeded the threshold for cCRT had better PFS than those below the threshold. Patients whose CD62Llow CD8+ T-cell proportion exceeded the threshold after durvalumab therapy showed prolonged PFS compared with those below the threshold.
Conclusions: cCRT promotes an increase in effector CD4+ T cells, and the subsequent increase in CD8+ T cells following durvalumab therapy prolongs PFS. Peripheral blood effector–type CD4+ and CD8+ T cells are potential biomarkers for evaluating the immune status of patients and predicting treatment efficacy.