Abstract: Objective To analyze the predictive value of quantitative parameters of PET/CT combined with hematological indexes for the prognosis in patients with advanced lung cancer treated by immune checkpoint inhibitor (ICI) combined with chemotherapy. Methods A total of 118 patients with advanced lung cancer admitted to our hospital were retrospectively included in this study. All patients received pembrolizumab injection combined with conventional chemotherapy for at least four consecutive periods (21 days as one period). The clinical efficacy was evaluated according to iRECIST criteria. Patients were divided into the clinical response group (n=70) and the non-response group (n=48). 18F-FDG positron emission tomography (PET) / CT was used to detect fixed standard uptake (SUV) max, SUVmean and SUVpeak, total tumor volume (MTV), total lesion glycolysis (TLG), and systemic load (MTVwb, TLGwb, SUVmeanwb and SUVmaxwb) before treatment. Data of neutrophil count, platelet count, albumin and neutrophil-lymphocyte ratio (NLR) were measured. PET/CT parameters and hematology results were compared between the two groups. Multivariate Logistic regression analysis was performed to analyze the risk factors influencing non-response in patients. Kaplan-Meier method was used to draw survival curves and the differences in cumulative survival rates were compared. Results Compared with the non-response group, SUVmax, MTV, MTVwb and NLR were significantly decreased in the response group (P＜0.05). Multivariate Logistic regression analysis showed that SUVmax ≥ 11.28 and NLR ≥ 5.97 were risk factors to the non-response (P＜0.05). The median follow-up time was 22.5 months (range, 6-30 months) and 69 patients survived (58.5%，69/118). Multivariate Cox regression analysis showed that SUVmax ≥11.28 and NLR ≥5.97 were closely related to OS (P＜0.05). Kaplan-Meier survival curve showed that cumulative survival rate was significantly lower in the high-risk group (SUVmax ≥11.28 and NLR ≥5.97) than that in the medium-risk group (SUVmax ≥11.28 or NLR ≥5.97) and the low-risk group (SUVmax ＜11.28 and NLR ＜5.97) (P＜0.01). Conclusion SUVmax value and serum NLR value detected by 18F-FDG PET/CT has good application value in predicting clinical efficacy and short-term prognosis in advanced lung cancer by ICI combined with chemotherapy.

Key words: lung neoplasms, positron emission tomography, tomography, X-ay computed, immune checkpoint inhibitors, fixed standard uptake, neutrophil-lymphocyte ratio, clinical response