External validation of a postoperative nomogram for the prediction of disease-specific survival in patients with papillary renal cell carcinoma using a large multicenter database

Purpose: Based on data retrieved from a comprehensive multicenter database, we externally validated a published postoperative nomogram for the prediction of disease-specific survival (DSS) in patients with papillary renal cell carcinoma (papRCC). Methods: A multicenter database containing data of 2325 patients with surgically treated papRCC was used as validation cohort. After exclusion of patients with missing data and patients included in the development cohort, 1372 patients were included in the final analysis. DSS-probabilities according to the nomogram were calculated and compared to actual DSS-probabilities. Subsequently, calibration plots and decision curve analyses were applied. Results: The median follow-up was 38 months (IQR 11.8–80.7). Median DSS was not reached. The c-index of the nomogram was 0.71 (95% CI 0.60–0.83). A sensitivity analysis including only patients operated after 1998 delivered a c-index of 0.84 (95% CI 0.77–0.92). Calibration plots showed slight underestimation of nomogram-predicted DSS in probability ranges below 90%: median nomogram-predicted 5-year DSS in the range below 90% was 55% (IQR 20–80), but the median actual 5-year DSS in the same group was 58% (95% CI 52–65). Decision-curve analysis showed a positive net-benefit for probability ranges between a DSS probability of 5% and 85%. Conclusions: The nomogram performance was satisfactory for almost all DSS probabilities; hence it can be recommended for application in clinical routine and for counseling of patients with papRCC.