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The To measure regulatory T cells (Tregs) expression in driver-gene-negative advanced non-small cell lung cancer (NSCLC) as well as its effect on the therapeutic efficacy and prognosis of immune checkpoint inhibitors (ICIs).

Fifty patients with advanced non-small cell lung cancer without driving genes who were receiving treatment with a monoclonal antibody targeting the programmed death receptor-1 (PD-1) made up the study group. 30 healthy subjects in the same period were chosen into the control group. Flow cytometry was used to identify CD4highCD25+Foxp3+Treg cells in peripheral blood of all participants. Relation between CD4highCD25+Foxp3+Treg cells and tumor markers were explored, and efficacy and prognosis in patients before and after therapy was analyzed.

The fraction of CD4highCD25+Foxp3+Treg cells in the study group was higher (P<0.05). Following three rounds of PD-1 monoclonal antibody treatment, patients' CD4highCD25+Foxp3+Treg cells proportion was lower than before treatment (P<0.01), and showed a positive correlation with tumor markers (P<0.05). The fraction of CD4highCD25+Foxp3+Treg cells in the CR+PR group decreased in both the second and third cycles after treatment compared to the SD+PD group (P<0.01), but no change was found before or during the first cycle (P>0.05). CD4highCD25+Foxp3+Treg cells proportion in the death group presented higher relative to the survival group (P<0.05). CD4highCD25+Foxp3+Treg cells predicted the area under the ROC curve was 0.8134, with significant difference (P<0.05).

CD4highCD25+Foxp3+Treg cells proportion in peripheral blood of NSCLC patients shows increased, and has predictive value for therapeutic efficacy of ICIs and prognosis of driver-gene-negative advanced NSCLC patients.