Preoperative nomograms for predicting extracapsular extension in Korean men with localized prostate cancer: a multi-institutional clinicopathologic study

Abstract

We developed a nomogram to predict the probability of extracapsular extension (ECE) in localized prostate cancer and to determine when the neurovascular bundle (NVB) may be spared. Total 1,471 Korean men who underwent radical prostatectomy for prostate cancer between 1995 and 2008 were included. We drew nonrandom samples of 1,031 for nomogram development, leaving 440 samples for nomogram validation. With multivariate logistic regression analyses, we made a nomogram to predicts the ECE probability at radical prostatectomy. Receiver operating characteristic (ROC) analyses were also performed to assess the predictive value of each variable alone and in combination. The internal validation was performed from 200 bootstrap re-samples and the external validation was also performed from the another cohort. Overall, 314 patients (30.5%) had ECE. Age, Prostate specific antigen (PSA), biopsy Gleason score, positive core ratio, and maximum percentage of biopsy tumor were independent predictors of the presence of ECE (all P values <0.05). The nomogram predicted ECE with good discrimination (an area under the ROC curve of 0.777). Our nomogram allows for the preoperative identification of patients with an ECE and may prove useful in selecting patients to receive nerve sparing radical prostatectomy.

Keywords: Nomograms; Patient Selection; Prostatectomy; Prostatic neoplasms.

Fig. 1

Receiver operating characteristics (ROC) curve of multivariate logistic regression model (MLRM) for predicting extracapsular extension (ECE) in prostate cancer.

Fig. 2

Nomogram for predicting ECE in localized prostate cancer. Find the position of each variable on the corresponding axis, draw a line to the 'points' axis for the number of points, add the points from all the variables together and draw a line from the 'total points' axis to determine the extracapsular extension probabilities at the bottom.

Fig. 3

(A) Calibration curves of preoperative nomogram in internal validation cohort. The x-axis is the predicted probability from the nomogram, and the y-axis is the actual probability of ECE. The dashed line represents performance of the ideal nomogram (predicted outcome perfectly corresponds with actual outcome). The dotted line represents the apparent accuracy of our nomogram without correction for over fit. The solid line represents bootstrap-corrected performance of our nomogram. (B) Calibration plot of nomogram in external validation cohort (n=440). Solid line indicates logistic calibration curve and dotted line represent data for validation cohort.