Abstract: ObjectiveTo observe the changes of T lymphocyte subsets and natural killer (NK) cells in patients with late stage nonsmall cell lung cancer (NSCLC) before and after treatment with PD1 inhibitor and its clinical effect. MethodsTotally 23 patients with NSCLC in Guangzhou Modern Hospital from January 2015 to January 2016 were collected. All patients were given 6 cycles of PD1 inhibitor treatment after chemotherapy or targeted drug treatment failure. Peripheral venous blood was collected before and after treatment to detect the percentage of CD3+, CD4+, CD8+ and NK cells in peripheral blood lymphocytes. The curative effects were evaluated by chest CT after treatment of 2, 4, 6 cycles. ResultsCompared with before treatment, the proportions of CD3+ (69.56%±7.81% vs. 63.91%±6.43%， t=2.679, P=0.005), CD4+ (39.01%±4.98% vs. 36.09%±4.77%, t=2.031, P=0.024) and CD4+/CD8+ (1.82±0.48 vs. 1.49±0.32, t=2.743, P=0.004) were increased after treatment, with significant differences. While compared with before treatment, the proportions of CD8+ (24.08%±5.13% vs. 26.04%±6.44%, t=1.142, P=0.130) and NK cells (22.68%±9.56% vs. 21.45%±10.01%, t=0.426, P=0.337) had little changes, with no significant differences. There were 3 patients with complete remission, 10 patients with partial remission, 8 patients with stable disease and 2 patients with progressive disease when completing 6 cycles of PD1 inhibitor treatment. Ten patients showed untoward effects such as mild sleepiness, thirst, tussis, pruritus and rash, and they were well tolerable. ConclusionPD1 inhibitor can improve the patient′s cellular immune function, and can achieve a more satisfactory shortterm efficacy and acceptable adverse reactions, which maybe bring new hopes for patients with NSCLC.

Key words: Immunosuppressive agents, Carcinoma, nonsmallcell lung, T lymphocyte subsets, Treatment outcome, PD1 inhibitor