Background: In recent years, immune checkpoint inhibitors (ICIs) have brought dramatic therapeutic effects on lung cancer. However, there are few reports regarding the therapeutic effect of ICIs on bone metastasis of non-small cell lung cancer (NSCLC). The purpose of this study was to investigate the therapeutic effects of ICIs on bone metastases of NSCLC and to analyze the predictors associated with ICI's response to them. Methods: This retrospective study analyzed NSCLC with bone metastases who initiated ICI treatment between 2016 and 2019. Clinical data was investigated and used as variables for analyzing the therapeutic effect predictors of ICIs. Blood sampling data were used within 1 week before ICI treatment initiation. The therapeutic effect of ICIs on bone metastases was evaluated by MD Anderson criteria (MDA criteria), and overall survival (OS) after the initiation of ICI treatment was investigated. Based on the evaluation of MDA criteria, univariate analysis was performed between the response group (CR+PR) and non-response group (SD+PD), and variables with p < 0.05 were used for multivariate logistic regression analysis to investigate the predictors associated with the therapeutic effect of ICIs. Results: The 55 patients were included comprising 40 males and 15 females (mean age of 66.3±7.9 years) and the mean follow-up period was 23.2 months. The response rate of ICIs to bone metastasis was 30.9% including 3 cases in CR and 14 cases in PR. The median survival time was 9.3 months, and the 1-year and 2-year survival rates were 40.6% and 19.3%, respectively. The OS was significantly longer in the response group than in the non-response group (p < 0.01). In the blood sampling data, the cutoff value of neutrophil-to-lymphocyte ratio (NLR) determined by receiver operating characteristic (ROC) curve analysis was 2.1. The multivariate analysis based on the variables with p < 0.05 in the univariate analysis revealed significant differences in sex, treatment line of ICIs, and NLR (Table). Conclusions: Treatment with ICIs showed favorable responses to bone metastasis and better prognosis in advanced NSCLC. Moreover, this study revealed that “female, NLR < 2.1, and first-line treatment of ICIs” were independent predictors associated with favorable response to bone metastasis.

Abbreviations: M male, F female, NLR neutrophil-to-lymphocyte ratio, CO cutoff value, OR odds ratio, CI confidence interval