ObjectiveTo evaluate the efficacy and safety of programmed cell death receptor 1 (PD-1) inhibitor combined with chemotherapy in the preoperative neoadjuvant treatment of stage Ⅲ non-small cell lung cancer (NSCLC).MethodsThe clinical data of 68 patients with stage Ⅲ NSCLC who underwent preoperative neoadjuvant treatment in our hospital from June 2019 to October 2020 were analyzed and divided into two groups according to a random number table. There were 34 patients in the control group including 19 males and 15 females with an average age of 59.41±4.77 years. In the observation group, there were 34 patients including 21 males and 13 females with an average age of 61.15±6.24 years. The patients in the control group were treated with albumin-bound paclitaxel and cisplatin for injection, and the patients in the observation group were treated with carrelizumab on the basis of the control group, and both groups received 2 cycles of preoperative neoadjuvant therapy. We compared the clinical efficacy of imaging, T lymphocyte subsets, drug side effects, surgical resection rate, major pathological remission (MPR), complete pathological remission (pCR) and postoperative complications of the two groups of patients, and analyzed the influencing factors for MPR.ResultsThe objective response rate (ORR) of imaging in the observation group (70.6%) was higher than that in the control group (38.2%, P<0.05). The positive rate of CD3+ cells, the positive rate of CD4+ cells, the positive rate of CD8+ cells and the ratio of CD4+/CD8+ cells in the observation group after treatment were higher than those in the control group (P<0.05). The drug toxicity of the observation group was higher than that of the control group in the reactive cutaneouscapillary endothelial proliferation (RCCEP)/rash, abnormal thyroid function, and abnormal myocardial enzymes (P<0.05). The MPR (66.7%) and pCR (51.9%) of the surgical observation group were higher than those of the surgical control group (MPR: 19.2%, pCR: 7.7%, P<0.05). There was no statistical difference in surgical resection rate and postoperative complications between the two groups (P>0.05). Univariate analysis showed that ECOG score, pathological type, neoadjuvant treatment plan and surgical resection were related to MPR (P<0.05). The results of binary logistic regression analysis showed that Eastern Cooperative Oncology Group (ECOG) score and neoadjuvant treatment plan were independent risk factors for MPR (P<0.05).ConclusionThe clinical efficacy of PD-1 inhibitor combined with chemotherapy in the preoperative neoadjuvant treatment of stage Ⅲ NSCLC patients is definite, and it can significantly improve the patients' MPR, pCR and cellular immune function, but the side effects caused by immunotherapy drugs need to be concerned.