External validation of existing nomograms predicting lymph node metastases in cystectomized patients

Abstract

© 2014, Japan Society of Clinical Oncology. Objectives: Karakiewicz et al. and Green et al. created pre-cystectomy nomograms to predict lymph node involvement. The aim of the study was to externally validate these two nomograms in intermediate-volume institutions in Europe. Patients and methods: Data from a Serbian single-centre cystectomy series comprising 183 patients with bladder cancer were used for the validation of two US nomograms, which were originally based on data from 726 and 201 patients, respectively. A multivariate regression model assessed the value of the clinical parameters integrated in the two nomograms. The expected predictive accuracy, calibration and clinical utility according to the nomograms were calculated. Results: Comparison of our dataset with the previously published data shows differences in nearly all underlying risk variables. Overall, 109 (59.6 %) patients had lymph node metastases. The analysis demonstrated that hydronephrosis and status of lymph nodes on computed tomography have independent prognostic value. The performance of the nomograms deteriorated from the development set, and the predictive accuracies for the two models showed moderate discriminatory ability (61.2–69.1 %). In the decision curve analysis, only the Green et al. model predicting lymph node positivity provided net benefit. Conclusions: The Green et al. nomogram seems applicable to patients from Europe, despite varying risk factors in the validation dataset. Acceptance of such a tool into daily clinical management may lead to more appropriate decision-making. Nevertheless, further improvement and implementation of novel statistical models with enhanced predictive accuracy is needed.