Real-life performance of imaging vs. nomograms for the assessment of lymph-node involvement in prostate cancer: Should we trust radiology?

Introduction & Objectives: To assess the performance of different imaging modalities and nomograms for lymph node staging in clinical node positive (cN1) prostate cancer (PCa) patients treated with radical prostatectomy (RP) and pelvic lymph node dissection (PLDN). Materials & Methods: We relied on a multicentric database of 336 consecutive cN1 patients from 16 Academic institutions treated with RP+PLND from 2009 to 2022. We calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy and AUC (Youden’s J) of abdominal CT scans, MRIs, Choline-PET, PSMA-PET, Briganti’s nomogram and Gandaglia’s nomogram. For both nomograms, a cut-off of nodal involvement of 7% was used to define clinical lymph node positivity, according to previous literature. Results: Overall, median age was 67 years, median PSA at diagnosis was 10 ng/mL and harbored biopsy grade group 1, 2, 3, 4, and 5 in respectively 12%, 14%, 21%, 32% and 21%. LND was extended to obturator+external iliac artery (OA+EIA) in 21%, to internal iliac artery (OA+EIA+IIA) in 29%, until common iliac artery (OA+EIA+IIA+CIA) in 28%, and to presacral artery (OA+EIA+IIA+CIA+PreSA) in 22%. At final pathology, 193 (57%) patients were pN0 vs 143 (43%) pN1. Sensitivity for CT, MRI, Choline-PET, PSMA-PET, Briganti and Gandaglia was 75% (67-82%), 16% (10-23%), 4% (1-8%), 13% (8-19%), 94% (87-98%), and 94% (85-98%), respectively. Specificity for CT, MRI, Choline-PET, PSMA- PET, Briganti and Gandaglia was 26% (20-33%), 84% (78-89%), 97% (94-99%), 85% (80-90%), 29% (21-39%), and 28% (19-38%), respectively. Performance, measured by Youden’s J, was 51% (50-51%), 50% (50-51%), 50% (50-51%), 49% (48-49%) , 62% (61-63%), and 61% (60-62%) for respectively CT, MRI, Choline-PET, PSMA-PET, Briganti and Gandaglia. Conclusions: Our study suggests that clinical nodal staging in PCa is still suboptimal. In this context, Briganti’s and Gandaglia’s nomograms, when used to define cN1 PCa, might outperform imaging modalities. Therefore, nomograms should be considered in treatment planning, even outside the surgical context.