Background: In recent years, advanced lung cancer patients who received immune checkpoint inhibitors (ICIs) reportedly had a more prolonged overall survival (OS) than those treated with conventional anticancer drugs. However, the therapeutic effect of ICIs on bone metastases remains unclear. The purpose of this study was to investigate the therapeutic effects of ICIs on advanced lung cancer with bone metastasis. Methods: This retrospective study included 58 lung cancer patients (42 men and 16 women; mean age, 66.2±7.8 years) who had been diagnosed with bone metastasis before the initiation of ICI treatment between 2016 and 2019, and the mean follow-up period was 23.2 months. The clinical data such as content of chemotherapy including the bone-modifying agent (BMA), skeletal-related events (SREs), and immune-related adverse events (irAEs) were investigated. The therapeutic effects of ICIs on the primary lung lesions and bone metastases were evaluated by the response evaluation criteria in solid tumors 1.1 (RECIST 1.1) and MD Anderson criteria, respectively. To assess the influence of ICI treatment on prognosis, OS from the diagnosis of bone metastases was compared to the prognostic prediction of Katagiri's score. Results: The most used ICI was pembrolizumab in 27 cases (46.6%). BMA was used in 38 cases (65.6%), and denosumab was used in 31 cases (81.6%). SREs and irAEs were observed in three cases (5.2%) and 13 cases (22.4%), respectively. In the primary lung lesions, the response rate (RR) and disease control rate (DCR) of ICIs were 14.3% and 38.1%, respectively, including one case in CR and 5 cases in PR. In the bone metastatic lesions, the RR and DCR were 38.6% and 75.0%, respectively, including 3 cases in CR and 14 cases in PR. In 17 cases that ICIs responded to bone metastases, nine cases were treated with pembrolizumab (52.9%), and all cases whose evaluations were CR had been treated with concomitant therapy of pembrolizumab and denosumab. The median survival time was 28.1 months and the 2-year OS rate was 51.7%. The 6-, 12-, and 24-month OS rates in this study were more favorable than the prognostic prediction of the Katagiri's score. Conclusions: ICI treatment showed favorable responses to bone metastases in NSCLC and better prognoses than conventional predictive prognosis. Particularly, pembrolizumab may be the most effective, and the therapeutic effect was enhanced by the concomitant use of denosumab.

Abbreviations: RECIST 1.1 response evaluation criteria in solid tumors 1.1, MDA criteria MD Anderson criteria, CR complete response, PR partial response, SD stable disease, PD progressive disease