Objective To analyze the impact of lymphocyte subsets on chemotherapy efficacy and long-term survival of patients with advanced non-small cell lung cancer(NSCLC).Methods Totally 125 NSCLC patients who had received first-line chemotherapy including paclitaxel and pemetrexed with/without platinum were enrolled in this study.Lymphocytes from peripheral blood were collected before and after two cycles of first-line chemotherapy.Flow cytometry was performed to determine the expressions of 21 fluorescence-labeled lymphocyte subsets.Based on the imaging findings,chemotherapy efficacy was evaluated,and impact of the lymphocyte subsets on progression-free survival(PFS)and overall survival(OS)were analyzed.Results The baseline peripheral lymphocyte subsets showed no significant difference among groups receiving different treatment protocols(all P>0.05).After 2 cycles of chemotherapy,the percentage of CD4+CD29+lymphocytes was(16.87±5.28)% in progressive disease group,which was significantly lower than those in complete remission+partial remission group [(22.42±7.88)%,P=0.013] and stable disease group [(21.88±6.81)%,P=0.009].The median PFS was 7.07 months and median OS was 23.00 months.Cox multivariable regression analysis showed that the percentages of HLA-DR+(HR:1.03,95%CI:1.01-1.05,P<0.001) and CD3+HLA-DR+lymphocytes (HR:1.05,95%CI:1.01-1.08,P<0.001)were positively correlated with OS.Conclusions The rise of CD4+CD29+T lymphocytes in patients after chemotherapy indicates good chemotherapy efficacy.Higher percentage of HLA-DR+and CD3+HLA-DR+lymphocytes in peripheral blood before chemotherapy predicts favorable prognosis.