Nomograms are More Meaningful than Severity-Adjusted Institutional Comparisons for Reporting Outcomes

External validation of a pre-operative prognostic nomogram for renal cell carcinoma in two patient populations: a retrospective cohort study

The aim of this study was to establish the discriminating accuracy of Kanao's pre-operative nomogram for renal cell carcinoma in predicting cause-specific survival among representative patients who underwent nephrectomy. Patients originated from two centers: Chiba University Hospital (n= 151) and Chiba Cancer Center (n = 91). We validated the predictive accuracy, which was assessed using Harrell's concordance-index. The concordance-index values were 0.692 and 0.834 for Chiba University Hospital and Chiba Cancer Center, respectively, although it was 0.822 for the combined data sets. Results of external validation were different at each cohort. We constructed calibration plots of Kanao's nomogram and confirmed the tendency at each institution. Inconsistency of results among two centers makes it difficult to reach a valid conclusion. Therefore, the predictive accuracy of Kanao's nomogram was not settled. Clinicians need to confirm the predictive accuracy of Kanao's nomogram and construct calibration plots when applying this nomogram to different patient populations.

Low predictive accuracy of the Kattan postoperative nomogram for renal cell carcinoma recurrence in a population of French patients

BACKGROUND

The aim of the current study was to establish the predictive accuracy of the Kattan postoperative nomogram for nonmetastatic renal cell carcinoma (RCC) by comparing predictions with actual disease recurrence in patients who underwent surgery in a single center in France.

METHODS

Between 1985 and 2000, 844 patients were treated for RCC. The following data were collated: age, symptoms, histology, tumor size, grade, TNM 1997 stage, recurrence, and progression. For each patient a prognostic score (predicted probability) for recurrence-free survival (RFS) at 5 years was calculated using the Kattan nomogram. The discriminating ability of the model was assessed by Harrell's concordance index (c-index). Bootstrapping was used to assess confidence intervals. Furthermore, survival was then estimated by the Kaplan-Meier method and Cox proportional hazards regression analysis.

RESULTS

In all, 565 patients (median age, 62 years) were included. At the time of the last follow-up, 81 patients had died and 101 had experienced RCC recurrence. The c-index for RFS (Kattan nomogram) was only 0.607 (95% confidence interval [CI]: 0.576-0.635). The 5-year RFS rate and cancer-specific survival rate were 81.5% and 84.7%, respectively. Of the 4 variables included in the nomogram, only TNM stage was associated with recurrence in a multivariate analysis (Cox analysis) (P = .022).

CONCLUSIONS

There was a discrepancy between predicted RFS as estimated by the Kattan nomogram and the likelihood of being recurrence-free at 5 years according to the Cox analysis in the current population of patients. However, until new dynamic models become available clinicians may still improve their predictive ability by using the current nomogram.