Systemic Treatment of Bone Disease in Metastatic Urinary Malignancies

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.

Bone metastases from urothelial carcinoma. The dark side of the moon

Bone metastases are common in genitourinary cancers, but they are underreported and not well researched. Synchronous bone metastases occur in 1.39-5.5% of bladder cancer patients, while 30-40% of cases are metachronous. Bone morphogenetic proteins (BMPs) play a key role in regulating proliferation, migration and invasion of tumor cells in bone microenvironment of bone metastases from metastatic urothelial carcinoma (mUC). Bone metastases represent a poor prognostic factor due to high morbidity and mortality correlated to skeletal-related events (SREs). The incidence rate of SREs in bladder, renal pelvis, and ureteral cancer varies from 39 to 68%. Radiotherapy is the most frequent treatment for SREs. The early use of bone targeted therapies (BTT), zoledronic acid and denosumab, improves SREs incidence and morbidity and it seems to improve overall survival (OS). To date, several new agents (immunotherapy and targeted drugs) demonstrated efficacy in mUC. However, subgroup analysis for bone metastases is often not available, due to difficulties in analysing bone samples, non-RECIST lesions and delay in systemic treatment due to SREs that limit the enrolment of bone mUC patients in clinical trials. Larger solid tumor studies that included UC patients are the main source of data for the management of mUC patients with bone metastases. For these patients, multidisciplinary approach should be preferred, involving orthopaedics, radiotherapists and rehabilitation to improve outcome and quality of life. New prospective trials should characterize clinical and molecular features of patients with bone metastases and the impact of new drugs on this poor prognostic metastatic site.