External validation of the Mayo Clinic cancer specific survival score in a Japanese series of clear cell renal cell carcinoma

Purpose: We validated the Mayo Clinic SSIGN (stage, size, grade and necrosis) score in an independent Japanese sample of patients. Materials and Methods: Between 1985 and 2006, 406 consecutive Japanese patients underwent nephrectomy for clear cell renal cell carcinoma. The prognostic value of pathological features for disease specific survival was evaluated using the Cox proportional hazards regression model. The predictive ability of the SSIGN score was evaluated using the concordance index. Results: Median followup in the 406 patients was 56 months. Of the patients 100 died of renal cell carcinoma and the 5-year cancer specific survival rate was 78.4%. All features comprising the SSIGN score were significantly associated with death from renal cell carcinoma on univariate analysis. Primary tumor classification, regional lymph node involvement, distant metastasis and Fuhrman nuclear grade were significantly associated with death from renal cell carcinoma in a multivariate setting. The median SSIGN score in the 406 patients was 3 (range 0 to 15). The concordance index of the SSIGN score was 0.814. The 5-year cancer specific survival rate in patients with a score of 0 to 2, 3 or 4, 5 or 6, 7 to 9 and 10 or more was 96.8%, 92.5%, 78.8%, 57.7% and 18.1%, respectively. The survival rate in the latter 3 groups was higher than reported rates in American and European patients. Conclusions: The Mayo Clinic SSIGN score can be applicable to Japanese patients with renal cell carcinoma with a high degree of prognostic accuracy. Future studies are needed to determine whether Japanese patients with moderate and high SSIGN scores survive longer than their American and European counterparts.