Assessing the most accurate formula to predict the risk of lymph node metastases from prostate cancer in contemporary patients treated with radical prostatectomy and extended pelvic lymph node dissection

Background and purpose The aim of this study was to perform a head-to-head comparison of the Roach formula vs. two other newly developed prediction tools for lymph node invasion (LNI) in prostate cancer, namely the Nguyen and the Yu formulas. Material and methods We included 3115 patients treated with radical prostatectomy and extended pelvic lymph node dissection (ePLND), between 2000 and 2010 at a single center. The predictive accuracy of the three formulas was assessed and compared using the area-under-curve (AUC) and calibration methods. Moreover, decision curve analysis compared the net-benefit of the three formulas in a head-to-head fashion. Results Overall, 10.8% of patients had LNI. The LNI-predicted risk was >15% in 25.5%, 3.4%, and 10.2% of patients according to the Roach, Nguyen and Yu formula, respectively. The AUC was 80.5%, 80.5% and 79%, respectively (all p > 0.05). However, the Roach formula demonstrated more favorable calibration and generated the highest net-benefit relative to the other examined formulas in decision curve analysis. Conclusions All formulas demonstrated high and comparable discrimination accuracy in predicting LNI, when externally validated on ePLND treated patients. However, the Roach formula showed the most favorable characteristics. Therefore, its use should be preferred over the two other tools.