Objective:To investigate the relationship between KRAS gene mutation, programmed death receptor ligand 1 (PD-L1) expression and prognosis of first-line concurrent chemoradiotherapy in patients with locally advanced non-small cell lung cancer.Methods:The clinical data of 50 patients with locally advanced non-small cell lung cancer who were admitted to Nanping First Hospital from January 2018 to December 2021 were retrospectively analyzed. All patients were treated with first-line concurrent chemoradiotherapy. Tissue samples of patients were obtained and paraffin embedded before treatment. Real-time fluorescence quantitative polymerase chain reaction was used to detect the type of KRAS gene mutation in tissues before treatment, and the expression of PD-L1 was determined by immunohistochemistry (the percentage of positive cells in tumor cells ≥1% was positive), and the relationship between KRAS gene status, PD-L1 expression and clinical characteristics and short-term efficacy of patients was analyzed. Patients were followed up for 1 year, and progression-free survival (PFS) curves were plotted by Kaplan-Meier method, and log-rank test was used for comparison. Univariate and multivariate Cox proportional hazards models were used to analyze the influencing factors of PFS.Results:Among the 50 patients, 11 (22.00%) were KRAS mutant, and 36 (72.00%) were PD-L1 positive. Among the 11 patients with KRAS mutation, there were 2 cases of codon 13 mutation and 9 cases of codon 12 mutation in exon 2. The objective response rate (ORR) and clinical control rate (DCR) were 76.00% (38/50) and 86.00% (43/50). There were no significant differences in patients' age, pathological type, TNM stage, ORR and DCR between KRAS mutant group and KRAS wild type group (all P > 0.05). The proportions of male patients [72.73% (8/11) vs. 38.46% (15/39)], patients with smoking history [90.91% (10/11) vs. 20.51% (8/39)] and patients with PD-L1 positive expression [100.00% (11/11) vs. 64.10% (25/39)] in KRAS mutant group were higher than those in KRAS wild type group (all P < 0.05). There were no significant differences in patients' age, pathological type, gender, smoking history, TNM stage, ORR and DCR between PD-L1 positive group and PD-L1 negative group (all P > 0.05). The median PFS time of patients in KRAS mutant group and wild type group was 8.75 and 11.32 months, and the difference in PFS between the two groups was statistically significant ( P = 0.039). The median PFS time of patients with PD-L1 positive and negative was 10.19 and 11.16 months, and there was no statistical significance in PFS between the two ( P = 0.116). Multivariate Cox regression analysis showed that KRAS gene mutation was an independent risk factor for PFS in patients with locally advanced NSCLC after first-line concurrent chemoradiotherapy ( HR = 1.449, 95% CI 1.071-1.196, P = 0.017). PD-L1 expression, smoking history and gender were not independent influencing factors for PFS (all P > 0.05). Conclusions:KRAS gene status is closely related to the prognosis of patients with locally advanced non-small cell lung cancer treated with first-line concurrent chemoradiotherapy, while PD-L1 expression is not.