Abstract
PURPOSE: The purpose of this study was to assess the incidence of and the risk factors and prognostic factors for bone metastasis (BM) in initial metastatic renal cell carcinoma (RCC) based on a large population analysis. PATIENTS AND METHODS: Data were obtained for a total of 45,824 RCC patients recorded in the database of the Surveillance, Epidemiology, and End Results program of the National Cancer Institute between 2010 and 2014. Multivariate logistic and Cox regression analyses were used to identify the risk factors and prognostic factors associated with BM in RCC patients. Kaplan-Meier analysis was used to estimate the overall survival of RCC patients, and the difference between the survival curves was tested by log-rank tests. RESULTS: A total of 1,509 (3.29%) patients were diagnosed with bone metastases at initial diagnosis. Male gender, higher T stage, lymph node involvement, poor tumor grade, presence of lung, liver, and brain metastases, and the collecting duct type of RCC were positively associated with BM occurrence. The median survival time for RCC patients with bone metastases was 12.0 (95% confidence interval [CI]: 10.69-13.31) months, and the survival time for those with collecting duct, clear-cell, papillary, and chromophobe subtypes of RCC were 3 (95% CI: 0.23-5.77), 13 (95% CI: 11.60-14.40), 8 (95% CI: 5.09-10.91), and 11 (95% CI: 5.02-16.98) months; these differences were significantly different (P<0.01). Older age, higher T stage, lymph node involvement, poor tumor grade, the presence of lung, liver, and brain metastases, collecting duct RCC, and the absence of surgical treatments were the factors associated with worse prognoses. CONCLUSION: BM was highly prevalent and significantly decreased the survival rate of RCC patients. A number of factors associated with the development and prognosis of BM were identified, and these insights provide preventive guidelines for screening and treatment of BM in RCC patients.