A novel nomogram provides improved accuracy for predicting biochemical recurrence after radical prostatectomy

Abstract

Background: Various prediction tools have been developed to predict biochemical recurrence (BCR) after radical prostatectomy (RP), however, few of the previous prediction tools used serum prostate specific antigen (PSA) nadir after RP and maximum tumor diameter (MTD) at the same time. In this study, a nomogram incorporating MTD and PSA nadir was developed to predict BCR-free survival. Methods: 337 patients who underwent RP were retrospectively enrolled in this study. The maximum diameter of the index lesion was measured on magnetic resonance imaging (MRI). Cox regression analysis was performed to evaluate independent predictors of BCR. A nomogram was subsequently developed for the prediction of BCR-free survival at 3 and 5 years after RP. Time-dependent receiver operating characteristic (ROC) curve and decision curve analysis were performed to identify the advantage of the new nomogram in comparison with the CAPRA-S score. Results: A novel nomogram was developed to predict BCR by including PSA nadir, MTD, Gleason score, surgical margin (SM), and seminal vesicle invasion (SVI), since these variables were significantly associated with BCR in both univariate and multivariate analysis (p <0.05). In addition, a basic model including Gleason score, SM, and SVI was developed and used as a control to assess the incremental predictive power of the new model. The concordance index of our model was slightly higher than CAPRA-S model (0.76 vs. 0.70, p =0.02) and it was significantly higher than that of the basic model (0.76 vs. 0.66, p =0.001). Time-dependent ROC curves and decision curve analyses also demonstrated the advantages of the new nomogram.Conclusions: PSA nadir after RP and MTD based on MRI before surgery are independent predictors of BCR. By incorporating PSA nadir and MTD into the conventional predictive model, our newly developed nomogram significantly improved the accuracy in predicting BCR-free survival after RP.