(UroToday.com) The authors evaluate the negative predictive value and SUVmax characteristics of PSMA PET/CT to help avoid the need for pelvic lymph node dissection (PLND) at the time of radical prostatectomy (RP). Historically, nomograms dictated the need for PLND at the time of RP. But, their AUCs were typically between 0.5-0.6 for predicting node positive disease. As the authors note, prostate-specific membrane antigen positron-emission-tomography (PSMA-PET) scan is increasingly being utilized for staging prostate cancer (PCa). In fact, it is quickly replacing traditional imaging, particularly for high risk disease.
Therefore, the authors sought to evaluate the accuracy of the PSMA-PET scan with the aim of identifying patients who could be spared a pelvic lymph node dissection (PLND) at the time of radical prostatectomy (RP). To that effect, they retrospectively reviewed patients who underwent a PSMA-PET scan followed by an RP with extended PLND (external iliac, obturator and common iliac nodes) at their tertiary cancer care center between Aug 2015 and September 2022.
Patients were classified as clinically node negative or positive (cN0 or cN+) based on the PSMA PET scan. The nodal status in the PSMA-PET scan was compared with the final histopathology of the PLND (pN0 or pN+).
They included 205 patients. Patients were stratified as follows based on MRI and PSMA-PET scans: 6 (2.9%) low-risk, 49 (23.9%) intermediate-risk, 46 (22.4%) high-risk localized, 89 (43.4%) locally-advanced node-negative and 15 (7.3%) node-positive patients.
The sensitivity, specificity, positive predictive value, and negative predictive value of the PSMA PET scan for nodal status were 37.5%, 98.2%, 80% and 89.4% respectively. The NPV was 89.4%, 93.8%, 87% and 86.6% for overall, intermediate-risk, high-risk localized and locally-advanced node-negative patients respectively.
The median SUVmax of the primary prostate lesion in patients who were true negatives for nodes, as identified by the PSMA-PET scan, was significantly lower (12.8 vs 26.4, p<0.001) than that in patients who were false negative (cN0 on PSMA but pN+ in final pathology).
Of the 190 cN0 patients, 20 had a false negative PSMA PET scan. Three of the 49 intermediate-risk patients had a false negative PSMA PET scan for nodes; the SUVmax scores of their prostate lesions were 26.59, 40.06 and 54.55 which were much higher than the median SUVmax score (12.8) in patients with a true negative scan. For the 135 high-risk cN0 patients, the 17 false negative patients had a median SUVmax of 24.37 compared to those with a true negative scan (13.57), p<0.001.
Based on this, the authors conclude that the high NPV of PSMA-PET scan coupled with evaluation of the SUVmax of the primary prostatic lesion can help avoid a PLND in intermediate and high-risk patients with a ‘negative’ PSMA-PET scan. The results can be considered as hypothesis generating and indicate the use of PSMA as a biomarker for predicting nodal disease. Further larger studies can help determine the ideal cut-off values for the SUVmax of the primary lesion.
Presented by: Gagan Prakash, MD, Tata Memorial Centre
Written by: Thenappan (Thenu) Chandrasekar, MD – Urologic Oncologist, Associate Professor of Urology, University of California, Davis @tchandra_uromd @UCDavisUrology on Twitter during the 2023 American Urological Association (AUA) Annual Meeting, Chicago, IL, April 27 – May 1, 2023