Peripheral PD1-positive CD4 T-lymphocyte count can predict progression-free survival in patients with non-small cell lung cancer receiving immune checkpoint inhibitor

Background/Aim: Little information is available about the association between peripheral T-lymphocyte expression of programmed cell death protein 1 (PD1) and the efficacy of immune checkpoint inhibitor therapy in patients with non-small cell lung cancer (NSCLC). We analyzed the PD1 and cytotoxic T-lymphocyte associated protein 4 (CTLA4) expression in peripheral blood T-lymphocytes of patients with NSCLC receiving immune checkpoint inhibitor therapy. Patients and Methods: Patients with NSCLC who were scheduled to receive treatment with immune checkpoint inhibitors were prospectively enrolled in this study between November 2017 and November 2018. Peripheral blood samples were obtained within 1 week before or after the initiation of treatment with an immune checkpoint inhibitor. Results: Flow cytometry was conducted in 19 patients. Patients were treated with nivolumab, pembrolizumab, or atezolizumab. The group with a high percentage of PD1⁺CD4⁺ T-lymphocytes relative to the total CD4⁺ T-lymphocyte count had a longer progression-free survival [median=6.0 (95% confidence intervaI=0.5-not estimated) months] than the group with a low percentage of PD1⁺CD4⁺ T-lymphocytes [median=1.1 (95% confidence intervaI=0.4-5.0) months; p=0.034, log-rank test]. However, no significant associations were detected with the percentages of CTLA4⁺CD4⁺, PD1⁺CD8⁺ or CTLA4⁺CD8⁺ T-lymphocytes in the peripheral blood. Conclusion: A high percentage of peripheral CD4⁺PD1⁺ T-lymphocytes was associated with a longer progression-free survival in patients receiving treatment with an immune checkpoint inhibitor. The systemic immune system may have an influence on the efficacy of immune checkpoint inhibitor therapy in patients with NSCLC.