External Validation and Addition of Prostate-specific Membrane Antigen Positron Emission Tomography to the Most Frequently Used Nomograms for the Prediction of Pelvic Lymph-node Metastases: an International Multicenter Study.

ABSTRACT

BACKGROUND: Different nomograms exist for the preoperative prediction of pelvic lymph-node metastatic disease in individual patients with prostate cancer (PCa). These nomograms do not incorporate modern imaging techniques such as prostate-specific membrane antigen (PSMA) positron emission tomography (PET). OBJECTIVE: To determine the predictive performance of the Briganti 2017, Memorial Sloan Kettering Cancer Center (MSKCC), and Briganti 2019 nomograms with the addition of PSMA-PET in an international, multicenter, present-day cohort of patients undergoing robot-assisted radical prostatectomy (RARP) and extended pelvic lymph-node dissection (ePLND) for localized PCa. DESIGN, SETTING, AND PARTICIPANTS: All 757 eligible patients who underwent a PSMA-PET prior to RARP and ePLND in three reference centers for PCa surgery between January 2016 and November 2020 were included. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Performance of the three nomograms was assessed using the receiver operating characteristic curve-derived area under the curve (AUC), calibration plots, and decision curve analyses. Subsequently, recalibration and addition of PSMA-PET to the nomograms were performed. RESULTS AND LIMITATIONS: Overall, 186/757 patients (25%) had pelvic lymph-node metastatic (pN1) disease on histopathological examination. AUCs of the Briganti 2017, MSKCC, and Briganti 2019 nomograms were 0.70 (95% confidence interval [95% CI] 0.64-0.77), 0.71 (95% CI 0.65-0.77), and 0.76 (95% CI 0.71-0.82), respectively. PSMA-PET findings showed a significant association with pN1 disease when added to the nomograms (p < 0.001). Addition of PSMA-PET substantially improved the discriminative ability of the models yielding cross-validated AUCs of 0.76 (95% CI 0.70-0.82), 0.77 (95% CI 0.72-0.83), and 0.82 (95% CI 0.76-0.87), respectively. In decision curve analyses, the addition of PSMA-PET to the three nomograms resulted in increased net benefits. CONCLUSIONS: The addition of PSMA-PET to the previously developed nomograms showed substantially improved predictive performance, which suggests that PSMA-PET is a likely future candidate for a modern predictive nomogram. PATIENT SUMMARY: Different tools have been developed to individualize the prediction of prostate cancer spread to lymph nodes before surgery. We found that the inclusion of modern imaging (prostate-specific membrane antigen positron emission tomography) improved substantially the overall performance of these prediction tools.