Assessing the accuracy and generalizability of the preoperative and postoperative Karakiewicz nomograms for renal cell carcinoma: results from a multicentre European and US study

Abstract

To assess the accuracy and generalizability of the pre- and postoperative Karakiewicz nomograms for predicting cancer-specific survival (CSS) in patients with renal cell carcinoma (RCC). This retrospective study included 3231 patients from European and US centres, who were treated by radical or partial nephrectomy for RCC between 1992 and 2010. Prognostic scores for each patient were calculated and the primary endpoint was CSS. Discriminating ability was assessed by Harrell's c-index for censored data. The 'validation by calibration' method proposed by Van Houwelingen was used for checking the calibration of covariate effects. Calibration was graphically explored. Local and systemic symptoms were present in 23.2% and 9.1% of the patients, respectively. The median follow-up (FU) was 49 months. At the last FU, 408 cancer-related deaths were recorded, Kaplan-Meier estimates of CSS (with 95% confidence intervals [CIs]) at 5 and 10 years were 0.86 (0.84-0.87) and 0.77 (0.75-0.80), respectively. Both nomograms discriminated well. Stratified c-indices for CSS were 0.784 (95% CI 0.753-0.814) for the preoperative nomogram, and 0.842 (95% CI 0.816-0.867) for the postoperative one, with a significant difference between the two values (P < 0.001). The covariate-based predictions on our data for both nomograms were valid. The calibration plots showed no relevant departures from ideal predictions. The results suggest that the postoperative Karakiewicz nomogram discriminates substantially better than the preoperative one. These nomogram-based predictions may be used as benchmark data for pretreatment and postoperative decision-making in patients at various stages of RCC.