External validation of a preoperative nomogram for prediction of the risk of recurrence after radical prostatectomy.
ABSTRACT To test the validity of an updated version of the preoperative Kattan nomogram for prediction of recurrence after radical prostatectomy (RP), published by Stephenson et al.
We relied on clinical and postoperative prostate-specific antigen follow-up data of 1978 patients treated with open RP at our institution between 1992 and 2006. The accuracy of the nomogram-derived recurrence-free survival predictions were separately tested at 1 to 10 years after RP. Moreover, the relationship between the nomogram-predicted recurrence-free survival rate and the observed recurrence-free survival rate was graphically explored in calibration plots.
Median follow-up of censored patients was 32 months. For nomogram-derived recurrence-free survival predictions at 1 to 10 years, the accuracy of the nomogram ranged from 70% to 76%. The calibration between the predicted and observed recurrence-free survival rates was good at 1 and 2 years after RP. However, at all other examined time points, departures from ideal predictions were recorded.
Our findings indicate that the preoperative biochemical recurrence nomogram reported by Stephenson et al. can be applied to European patients with good accuracy. However, its calibration was only suboptimal for predictions made 3 or more years after RP, with a tendency to overestimate the probability of recurrence-free survival. This potential limitation should be considered when this tool is applied to European patients.