Development and External Validation of a Multiparametric Magnetic Resonance Imaging and International Society of Urological Pathology Based Add-On Prediction Tool to Identify Prostate Cancer Candidates for Pelvic Lymph Node Dissection

Abstract

To expand the current prediction tools for lymph node invasion (LNI) in prostate cancer (PCa) patients with today's state-of-the-art available tumor information, including multiparametric MRI (mpMRI)-based tumor (T) staging and detailed biopsy information. Materials and methods: PCa patients with registered ISUP-based biopsy information and mpMRI information, who underwent a radical prostatectomy with extended pelvic LN dissection, were selected. A LNI prediction tool was developed in 420 patients and externally validated in 187 patients. A concordance index was estimated to quantify the discriminative performance of the model. Results: In the development cohort, a median of 21 LN was removed per patient. Seventy one patients (16.9%) were diagnosed with LNI. Statistically significant predictors of LNI were the iPSA value, mpMRI-based T-stage, maximum tumor-length-in-one-core (mm) and ISUP grade group corresponding to the maximum tumor-involvement-in-one-core. The predictive accuracy of this LNI prediction tool was 79.7% after 5-fold internal cross validation and 72.5% at external validation. Conclusion: We report a contemporary, externally validated prediction tool for the presence of LNI in PCa patients. This prediction tool answers to the paradigm shift from systematic biopsies towards targeted biopsies by incorporating additional core-specific biopsy information instead of the percentage of positive cores. This new tool will also overcome stage migration, which is a potential risk when mpMRI information is used in digital rectal exam based nomograms.

External validation of the Memorial Sloan Kettering Cancer Centre and Briganti nomograms for the prediction of lymph node involvement of prostate cancer using clinical stage assessed by magnetic resonance imaging

“…Recently, two new nomograms have been introduced, including mpMRI and target biopsy features such as maximum diameter of the index lesion and maximum percentage of tumour involvement in one core [24,25]. Of these, the 2019 Briganti nomogram was recently externally validated, showing excellent characteristics, including an AUC of 79% and high agreement between predicted and observed probabilities for risk thresholds below 35% [26].…”

“…Overall, 301 patients (28%) had histologically confirmed LNI. The median number of lymph nodes removed was 20 (interquartile range [13][14][15][16][17][18][19][20][21][22][23][24][25]. A total of 21 patients (2%) had one or more covariates missing, including DRE T-stage (N = 11), mpMRI T-stage (N = 2), and biopsy data (N = 8).…”

“…Huang et al [23] demonstrated that addition of PI-RADS score improved model discrimination in terms of AUC for both nomograms, increasing from 75% to 86% for Briganti and from 79% to 88% for MSKCC, respectively. Recently, two new nomograms have been introduced, including mpMRI and target biopsy features such as maximum diameter of the index lesion and maximum percentage of tumour involvement in one core [24,25]. Of these, the 2019 Briganti nomogram was recently externally validated, showing excellent characteristics, including an AUC of 79% and high agreement between predicted and observed probabilities for risk thresholds below 35% [26].…”

“…In their head-to-head comparison, the 2019 Briganti nomogram outperformed the Briganti 2017 and MSKCC 2018 nomograms in terms of discrimination, calibration and net benefit. Although these new nomograms potentially enable improved LNI risk prediction due to the addition of mpMRIguided target biopsy, they both include complex features which may not always be available in clinical practice, such as maximum diameter of the index lesion on mpMRI and highest tumour length in millimetres of all biopsy cores taken [24,25]. In addition, more external validation studies are warranted to confirm the accuracy of these new nomograms in external patient populations as model transportability needs to be adequate to prevent systematic wrong decisionmaking.…”

This Month in Adult Urology

“…Undoubtedly, continued updates will be required as new parameters are developed. In this issue of The Journal of UrologyÒ incorporation of mpMRI is evaluated with regard to prediction of the presence of clinically significant disease (page 713) 1 or pelvic lymph node metastasis (page 719). 2 Clinicians and patients often rely on prediction tools to help decide on treatment choices and, therefore, updates that include important variables such as mpMRI are essential.…”