External validation of an online nomogram in patients undergoing radical nephroureterectomy for upper urinary tract urothelial carcinoma

Background: The objective was to validate an online nomogram developed based on the French collaborative national database on upper urinary tract urothelial carcinoma (UUT-UC) using a different cohort. Methods: The study comprised 328 patients with UUT-UC who underwent radical nephroureterectomy. The discrimination of models was quantified using Harrell's concordance index. The relationship between the model-derived and actuarial cancer-specific mortality was graphically explored within calibration plots. Calibration was also assessed using the quartiles of the predicted survival at 3 and 5 years and calculation of the corresponding observed Kaplan-Meier estimates. Clinical net benefit was evaluated constructing decision curve analysis. Results: The discrimination accuracy of the nomograms at 3 and 5 years was 71.6% and 71.8%, respectively. Although nomograms discriminated well by Kaplan-Meier curves, and log-rank tests were all highly significant, the calibration plots tended to exaggerate the overestimation of mortality between predicted and observed probabilities at 3 and 5 years for survival. When compared with the AJCC/UICC staging system, the nomograms performed well across a wide range of threshold probabilities using decision curve analysis. Conclusion: The online nomogram is a highly accurate prognostic tool for patients with UUT-UC treated with radical nephroureterectomy. The model can provide an accurate estimate of the individual risk of cancer-specific mortality. Further improvement and implementation of novel molecular marker is needed.