Prognostic Factors for Renal Cell Carcinoma With Bone Metastasis: Who Are the Long-Term Survivors?

Purpose: Renal cell carcinoma is sometimes associated with bone metastasis. Several risk factors have been reported but some are still controversial. Also, the significance of laboratory tests has not been fully examined for such cases. Materials and Methods: We collected data on 94 renal cell carcinoma cases with bone metastasis treated at 3 tertiary referral centers. Clinicopathological parameters and outcome data were analyzed to search for predictors of overall survival retrospectively. The log rank test and the Cox proportional hazard model were used for univariate and multivariate analyses, respectively. Results: There were 64 males with a median age of 63.9 years. Histological diagnosis showed clear cell renal cell carcinoma in 63 patients, nonclear cell renal cell carcinoma in 7 and unclassified cancer in 6. Sarcomatoid differentiation was found in 17 cases. Metastasis was detected synchronously in 37 patients or metachronously at a median interval of 33.1 months. Multivariate analysis identified sarcomatoid differentiation (p = 0.001), vertebral bone involvement (p = 0.003), extraosseous metastasis (p = 0.021), alkaline phosphatase increased to 1.5 times the upper limit of normal (p = 0.0003) and C-reactive protein increased to greater than 0.3 mg/dl (p = 0.018) as significant risk factors. Cases were classified into 3 groups based on the number of risk factors, including low risk-28 with 0 or 1 risk factor, intermediate risk-26 with 2 risk factors and high risk-40 with 3 to 5 risk factors. This grouping clearly separated survival among these groups (each p < 0.001). It also confirmed the usefulness of the Memorial-Sloan Kettering Cancer Center classification system. Conclusions: Our risk classification incorporating 5 risk factors enables accurate prediction of survival, which can be helpful to make clinical decisions in cases of renal cell carcinoma with bone metastasis.