Abstract: Objective To explore the correlation between circulating lymphocyte profiles and the outcomes of non-small cell lung cancer (NSCLC) patients undergoing epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) therapy. Methods A retrospective cohort of 40 patients who received EGFR-TKI therapy at Peking Union Medical College Hospital was designed. Circulating lymphocyte subsets were collected using flow cytometry for dynamic monitoring during EGFR-TKI therapy. The survival of each patient was followed up by telephone call. The correlation of baseline and dynamic change of the peripheral blood circulating lymphocyte subsets and survival were further analyzed. Results Patients who responded to EGFR-TKI therapy had significantly higher baseline circulating CD4⁺CD45RA⁺CD62L⁺ T-cell counts during dynamic monitoring. The median progression-free survival (PFS) for the entire population was 27.1 months; however, overall survival (OS) was not achieved. The median PFS did not differ significantly between patients with higher and lower baseline CD4⁺CD45RA⁺CD62L⁺ T-cell counts. Furthermore, dynamic changes in CD4⁺CD45RA⁺CD62L⁺ T-cell counts were significantly correlated with not only the response to EGFR-TKI therapy response, but also PFS. PFS of patients with stable or increased CD4⁺CD45RA⁺CD62L⁺ T-cell counts during the EGFR-TKI therapy was significantly longer than that of patients with decreased CD4⁺CD45RA⁺CD62L⁺ T-cell counts (29.1 months vs. 9.4 months; P＜0.001). Conclusions Higher baseline circulating CD4⁺CD45RA⁺CD62L⁺ T-cell counts indicate a better EGFR-TKI response, and dynamic changes in CD4⁺CD45RA⁺CD62L⁺ T-cell counts are associated with prolonged PFS.

Key words: epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), lymphocyte subset, lung cancer, CD4⁺CD45RA⁺CD62L⁺ T cell, prognosis