Abstract: Objective  Tumor immunotherapy targeting programmed cell death ligand 1(PD1) receptor signal pathway has achieved a remarkableclinical outcomes on multiple types of tumors including nonsmall cell lung cancer(NSCLC). The study was to evaluate firstline therapy of two main PD1 inhibitors, pembrolizumab and nivolumab, with regard to activity and feasibility in advanced NSCLC in China. Methods  Two patients with advanced squamous NSCLC who had not received treatment previously were treated with intravenous pembrolizumab (100 mg every 3 weeks),  or nivolumab (2  mg/kg every 2 weeks),  respectively. Tumor response was assessed by RECIST v1.1 every one or two periods. Results  After treatment for 2 periods,  both patients experienced partial response (PR) of lung cancer,  and respiratory symptoms improved significantly and inflammation relieved. But unfortunately the patient treated with pembrolizum was observed brain metastates and finally died of the progressive brain metastases when assigning the 3rd treatment. The other patient treated with nivolumab was observed stable and obvious improvement of lung caner with PR,  but multiple brain metastases when assigned the 4th therapy which increased slightly when assigned the 5th treatment with stable disease (SD). During the immunotherapy,  the blood concentration of CA125 decreased significantly and no adverse reactions were observed in both patients. Conclusion  Preliminary studies have shown significant efficacy and safety by treatment with PD1 inhibitors in advanced primary NSCLC，and blood concentration of CA125 may be considered as an index of outcome. However,  PD1 inhibitors could not relieve the progression of brain metastases. And this conclusion needs to be verified by enrolling more patients and further study.

Key words: carcinoma, , nonsmallcell , lung, PD1 inhibitor; , pembrolizumab, nivolumab, immunotherapy