External Validation of the Mayo Clinic Stage, Size, Grade, and Necrosis (SSIGN) Score for Clear-Cell Renal Cell Carcinoma in a Single European Centre Applying Routine Pathology

BackgroundThe stage, size, grade, and necrosis (SSIGN) score has been created as an outcome prediction tool for clear-cell renal cell carcinoma (ccRCC) using review pathology.ObjectiveWe evaluated the prognostic accuracy of the SSIGN score model using routine pathology records.Design, setting, and participantsWe retrospectively evaluated pathology records of 1862 consecutive ccRCC patients with complete data including follow-up who had been operated between 1984 and 2006.InterventionSurgical treatment of patients with ccRCC.MeasurementsTNM stage, largest tumour diameter, tumour grade, and presence of histologic tumour necrosis were recorded. ccRCC were categorised according to the SSIGN-score algorithm as 0–15. Cancer-specific survival (CSS) was assessed using the Kaplan-Meier method for individual SSIGN-score categories (scores 0–1 and ≥10, respectively, were combined). For evaluation of the prognostic impact of stage, size, grade, and necrosis regarding CSS, a multivariate analysis using a Cox regression model was performed, and for assessment of prognostic accuracy, Harrell's concordance index was performed.Results and limitationsMedian tumour diameter was 5.0 cm (range: 0.6–22 cm). Tumour necrosis was noted in 607 tumours (32.6%). Median follow-up was 72.5 mo (range: 0–281 mo); 359 of 1862 patients (19.3%) died of RCC. Ten-year CSS rates for respective SSIGN scores in our study ranged from 96.5% (scores 0–1) to 19.2% (scores ≥10). pT categories, lymph-node status, distant metastases, high tumour grade (size ≥5 cm), and necrosis were each independent predictors of CSS. The Harrell's concordance index was 0.823. Limitations included smaller sample sizes in higher risk categories and limited numbers of patients at risk after 10 yr.ConclusionsOutcome prediction with the SSIGN score using routine pathology records was comparable to the original data based on review pathology. Combining scores into five categories improved discrimination. Our data support the routine use of the SSIGN score in clinical practice with regard to follow-up decisions and patient selection for adjuvant trials.