MP57-06: External validation and comparison of two nomograms predicting the probability of lymph node invasion in patients subjected to robotic radical prostatectomy and concomitant lymph node dissection

Nicola frego*, Paciotti Marco, Davide Maffei, Pier Paolo Avolio, Roberto Contieri, Alessandro Uleri, Massimo Lazzeri, Alberto Saita, Paolo Casale, Nicolò Maria Buffi, Giovanni Lughezzani, Milan, Italy

Introduction: Current guidelines recommend an extended Pelvic Lymph Node Dissection (ePLND) in Prostate Cancer (PCa) patients with a non negligible risk of Lymph Node Invasion (LNI), according to available nomograms. The Briganti 2012 nomogram has been recently updated in Briganti 2019, to include information on Magnetic Resonance Imaging (MRI) and targeted biopsy (TB). The aim of the study is to validate and compare Briganti 2012 and 2019 nomograms in an external cohort of contemporary patients.

Methods: We retrospectively collected data of consecutive patients treated with Robot Assisted Radical Prostatectomy and ePLND at our center, between December 2014 and August 2021. Data included clinical, MRI, and pathological characteristics. The risk of LNI was calculated with the published regression coefficients. The Receiver Operator Characteristics (ROC) curve and Area Under the Curve (AUC) were used to evaluate the accuracy, while deLong method was used to compare models' accuracy. Calibration plot was used to evaluate the extend of over and under estimation of the models. Multivariate Logistic Regression Analysis (MVA) was performed to evaluate potential predictive factors of LNI.

Results: Overall, we analyzed data on 842 patients. Of them, 377 (44.8%) underwent MRI and TB. Median age at surgery was 64 years (IQR 59-69) and median tPSA was 7.04 ng/mL (IQR 5.11-10.4). Extra Capsular Extension and Seminal Vesicles Invasion (SVI) at MRI were observed in 15.4% and 5.4% of patients, respectively. The median primary and secondary GS were 3 and 4, respectively. The median percentage of positive cores was 35% (IQR 21.4-50). Finally, median Gleason Group at TB was 2 (IQR 2-3) and the median percentage of clinically significant random cores was 21% (IQR 0-42). A median of 13 (IQR 9-18) nodes per patient were removed, and 85 (10.1%) patients had LNI at final pathology. The AUCs for Briganti 2012 and 2019 were 0.84 and 0.79, respectively. The calibration plots showed a good correlation between the predicted probabilities and the observed proportion of LNI for both models. In patients with both SB and TB, Briganti 2012 accuracy was 0.815, and no significant difference was found between the two nomograms (p = 0.66). At MVA only PSA > 20 ng/mL and the evidence of SVI at MRI were independent predictors of LNI.

Conclusions: The direct comparison of the two nomograms showed that Briganti 2019 nomogram was no more accurate than Briganti 2012, and that the role of MRI and MRI TB may be negligible in the prediction of LNI.

Source of Funding: None