Prognostic value of site-specific metastases and therapeutic roles of surgery for patients with metastatic bladder cancer: a population-based study

Background We aimed to evaluate the prognostic value of site-specific metastases in patients with metastatic bladder cancer and analyze the roles that surgeries play in the treatment of this malignancy. Materials and methods A population-based retrospective study using Surveillance, Epidemiology and End Results dataset was performed and metastatic bladder cancer patients were classified according to the sites of metastases (bone, brain, liver, lung and distant lymph nodes). Kaplan-Meier analysis with log-rank test was used for survival comparisons. Multivariate Cox regression model was employed to analyze the effect of distant metastatic sites on overall survival (OS) and cancer-specific survival (CSS). Results A total of 1862 patients with metastatic bladder cancer from 2010 to 2014 were identified. Bone, lung and distant lymph nodes were the most common metastatic sites. Patients with bone, brain, liver and lung involvement had worse OS and CSS compared to patients without the corresponding sites of metastases. Multivariate analysis showed that bone, brain, liver and lung metastases were independent prognostic factors for both OS and CSS, while distant node metastasis was not. Moreover, patients with a single metastatic site had more favorable OS (p<0.001) and CSS (p<0.001) than patients with multisite metastases. Among single-site metastatic patients, distant nodes and liver metastases represented the best and the worst prognosis, respectively. Moreover, radical cystectomy was an independent predictor for better OS and CSS, while in patients with liver metastasis and multiple metastatic sites, RC did not bring benefits. Besides, in patients with a single metastatic site, metastasectomy seemed to be associated with favorable OS (p=0.042), especially for patients with age <65 years (p=0.006) and for muscle-invasive bladder cancer patients (p=0.031). Conclusion Distant metastatic sites have differential impact on survival outcomes in patients with metastatic bladder cancer. Surgeries, including radical cystectomy and metastasectomy, might still lead to survival benefits for highly selected patients.