Abstract:Objective To investigate the relationship of the plasma cell-free DNA (cfDNA) levels with the efficacy of chemotherapy and the prognosis of patients with advanced non-small cell lung cancer (NSCLC).Methods Between January 2015 and January 2018, 148 patients with advanced NSCLC treated in our hospital were selected for the study. All the patients were treated with chemotherapy, and the chemotherapy efficacy of all patients were recorded. According to the clinical chemotherapy effect, the patients were divided into effective group (40 cases) and ineffective group (108 cases). The relationship between the general data and chemotherapy efficacy in patients with advanced NSCLC was analyzed. The plasma cfDNA levels of patients were compared between groups with different curative effects. The relationship between the plasma cfDNA levels before chemotherapy and the clinical characteristics of patients with advanced NSCLC was analyzed. Kaplan-Meier survival curve was used to analyze the relationship between the plasma cfDNA levels and the prognosis of patients with advanced NSCLC. COX regression was used to analyze the prognostic factors of patients with advanced NSCLC.Results The chemotherapy effect of advanced NSCLC patients without smoking history was better than that of advanced NSCLC patients with smoking history (P<0.05). After chemotherapy, the effective rate of 148 patients with advanced NSCLC was 27.03% (40/148). And the level of cfDNA in the effective group was significantly lower than that before chemotherapy and that in the ineffective group after chemotherapy (P<0.05). The level of cfDNA before chemotherapy was correlated with smoking history, tumor size and lymph node metastasis in patients with advanced NSCLC (P<0.05). The 24-month survival rate in the group with plasma cfDNA level <0.23 ng?μL-1 was significantly higher than that in the group with plasma cfDNA level ≥0.23 ng?μL-1 (P<0.05). The cfDNA level was an independent prognostic factor in patients with advanced NSCLC after chemotherapy (P<0.05).Conclusion Plasma cfDNA is expected to be an effective reference index for the evaluation of chemotherapy efficacy and prognosis in patients with advanced NSCLC.