Evaluating the utility of a preoperative nomogram for predicting 90-day mortality following radical cystectomy for bladder cancer
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OBJECTIVE: To evaluate the performance of the Isbarn nomogram for predicting 90-day mortality following radical cystectomy in a contemporary series. PATIENTS AND METHODS: We identified 1141 consecutive radical cystectomy patients treated at our institution between 1995 and 2005 with at least 90 days of follow-up. We applied the published nomogram to our cohort, determining its discrimination, with the area under the receiver operating characteristic curve (AUC), and calibration. We further compared it with a simple model using age and the Charlson comorbidity score. RESULTS: Our cohort was similar to that used to develop the Isbarn nomogram in terms of age, gender, grade and histology; however, we observed a higher organ-confined (≤pT2, N0) rate (52% vs 24%) and a lower overall 90-day mortality rate [2.8% (95% confidence interval 1.9%, 3.9%) vs 3.9%]. The Isbarn nomogram predicted individual 90-day mortality in our cohort with moderate discrimination [AUC 73.8% (95% confidence interval 64.4%, 83.2%)]. In comparison, a model using age and Charlson score alone had a bootstrap-corrected AUC of 70.2% (95% confidence interval 67.2%, 75.4%). CONCLUSIONS: The Isbarn nomogram showed moderate discrimination in our cohort; however, the exclusion of important preoperative comorbidity variables and the use of postoperative pathological stage limit its utility in the preoperative setting. The use of a simple model combining age and Charlson score yielded similar discriminatory ability and underscores the significance of individual patient variables in predicting outcomes. An accurate tool for predicting postoperative morbidity/mortality following radical cystectomy would be valuable for treatment planning and counselling. Future nomogram design should be based on preoperative variables including individual risk factors, such as comorbidities.
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