Clear cell renal cell carcinoma bone metastasis: What should be considered in prognostic evaluation

INTRODUCTION: Knowledge of clear cell renal cell carcinoma bone metastasis (ccRCC-BM) remains scarce. This study depicts clinical, pathological and outcome features of the disease and provides suggestions to establish prognosis prediction system more appropriate for ccRCC-BM. MATERIALS AND METHODS: Patients with ccRCC-BM had clinical, pathological data collected. Kaplan-Meier survival analysis was used for outcome profiles. Prognostic risks were evaluated using MSKCC/Motzer score. Univariate and multivariate logistic regression were performed to investigate association between clinical, pathological features and prognosis. RESULTS: In the series containing 106 ccRCC-BM patients with 4:1 male predominance, 44.3% of them had synchronous bone metastasis and 28.3% had multi-organ metastasis. Axial bone was prone to bone metastasis and the incidence of severe skeletal-related events was 54.7%. Curative bone lesion resection was performed in 70.7% patients. The median overall survival (mOS) time was 45 months for all and 32 months for those in unfavorable risk stratification. Shorter time to bone metastasis (TTBM) [OR 1.019, 95% CI (1.007, 1.031)], elderly age [OR 1.040, 95% CI (1.001, 1.080)], concomitant multi-organ metastasis [OR 3.883, 95% CI (1.375, 10.967)] and carbonic anhydrase (CA)-IX expression loss [OR 58.824, 95% CI (2.653, 1000)] were associated with poor prognosis. CONCLUSION: The outcome of ccRCC-BM remained poor in unfavorable risk stratification. Bone lesion resection accompanied by systematic therapy for selected patient could improve prognosis. Shorter TTBM, elderly age, concomitant multi-organ metastasis and the expression loss of CA-IX along with gender-bias, feasibility for surgical treatment are suggested to be incorporated in modified ccRCC-BM-specific prognosis prediction system.