Role of Bone Metastases in Patients Receiving Immunotherapy for Pre-Treated Urothelial Carcinoma: The Multicentre, Retrospective Meet-URO-1 Bone Study.

Background: Considerable numbers of patients with metastatic urothelial carcinoma (mUC) develop bone metastases (BoM). Their impact on the efficacy of immune-checkpoint inhibitors (ICIs) is not yet investigated.

Methods: Between July 2014 and August 2020 data on pts treated with single-agent ICIs after failure of at least 1 previous line of chemotherapy for advanced disease, were retrospectively collected across 14 Italian centers. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method. Cox regression analysis was performed evaluating potential prognostic factors for OS and PFS. Each factor was evaluated in univariable (UVA) and multivariable analysis (MVA).

Results: A total of 208 evaluable patients treated with ICIs were identified, including 122 (59%) without BoM (BoM-) and 86 (41%) with bone metastases (BoM+). After a median follow-up of 22.3 months, BoM+ patients showed shorter OS (median 3.9 vs 7.8 months, HR 1.59 [95%CI, 1.15-2.20], P = .005) and shorter PFS (median 2.0 vs 2.6 months, HR 1.76 [95%CI, 1.31-2.37], P < .001). Probability of being alive was 62% vs 40% after 6 months, 38% vs 23% after 1 year and 24% vs 13% after 2 years, in BoM- and BoM+ respectively. Within each Bellmunt score, OS and PFS of BoM+ patients were shorter. Both presence of BoM and higher Bellmunt risk score were significantly associated with shorter OS and PFS in UVA and MVA.

Conclusion: Patients treated with single-agent ICIs for BoM+ mUC have a dismal prognosis compared to BoM-. Further research is needed to understand the mechanism behind these outcomes.