LAUSR

e14153 Background: Monoclonal antibodies against the programmed cell death protein-1 (PD-1), e.g., nivolumab, have been shown to exhibit antitumor immunity and improve survival in patients with various cancers. Recently, it was reported that bone metastases are unlikely to respond to immunotherapy, while other reports have suggested that synergistic antitumor effect can be obtained by administration of denosumab in combination with PD-1 blockade using nivolumab. However, there are still very limited data on the efficacy and effects on the prognosis of nivolumab administered in combination with denosumab in patients with bone metastases. Methods: We reviewed the medical records and pharmacy database of patients who had received nivolumab plus denosumab treatment from April 2011 to March 2018 at our institution, in order to analyze the prognosis of patients with bone metastases from various cancers. The primary objective was to compare the progression-free survival between patients with and without bone metastases. The impact of combined nivolumab plus denosumab therapy was evaluated as an exploratory endpoint. Results: We extracted 201 patients who had received denosumab for bone metastasis and 45 patents who had received immune checkpoint inhibitor. We analyzed the data of 39 patients who had received nivolumab treatment; of these 39 patients, 10 had additionally also received denosumab for the treatment of bone metastases. The median age of the patients was 65 years (range 41-87); the primary disease was renal cell carcinoma in 17 patients, gastric cancer in 9 patients, melanoma in 6 patients, non-small cell lung cancer in 4 patients, and head and neck cancer in 3 patients. The median progression-free survival following treatment with nivolumab was 2.1 months in the group with bone metastases and 3.5 months in the group without bone metastases (log-rank test; p = 0.0779); the 6-month progression-free survival rate was 26.7% (95% CI: 21.6-69.2) in the patients with bone metastases and 39.3% (95% CI: 10.4-53.3) in those without bone metastases. Concurrent administration of denosumab, age, and the primary disease had no influence on the progression-free survival rate. Conclusions: This retrospective analysis revealed a trend towards lower immune responses in patients with bone metastases, even when nivolumab is administered in combination with denosumab. Immunotherapy for bone metastasis needs to be further explored.