(UroToday.com) The 2024 American Urological Association (AUA) annual meeting held in San Antonio, TX, was host to the advanced prostate cancer moderated poster session. Dr. Francesco Barletta presented the results of a multicentric cohort including 129 patients with molecular imaging (mi) node positive disease (miN1) undergoing radical prostatectomy with extended pelvic lymph node dissection (ePLND).
Dr. Barletta began by asserting the superiority of PSMA-PET as the most accurate imaging modality for nodal staging in prostate cancer as of 2024. However, they acknowledged significant variability in the accuracy of PSMA-PET in predicting N1 disease upon final histopathological analysis, some studies have reported positive predictive values spanning from 40 to 100%. They aimed to investigate the false positive rate of PSMA-PET (miN1) compared to preoperative lymph node involvement risk calculators/nomograms.
The study utilized data from 10 institutions spanning the years 2016 to 2023. PSMA-PET scans with miN1 findings, which were subsequently negative for lymph node involvement (pN0) upon final pathology after radical prostatectomy (RP) and extended pelvic lymph node dissection (ePLND), were classified as false positives. Biochemical recurrence (BCR) was defined as either a PSA level ≥0.1 ng/mL at 6 weeks after surgery or two consecutive PSA levels ≥0.2 ng/mL. For assessing preoperative lymph node involvement risk, the 2012 Briganti nomogram was employed.
This study comprised 129 individuals with miN1 disease on PSMA-PET before RP and ePLND. The majority, 94 (73%), had ISUP grade 4-5 disease at biopsy. All patients included exhibited nodal spots on PSMA-PET. Final pathology revealed pN0 disease in 88 (48%) patients. Dr. Barletta further elaborated that patients diagnosed with pN1 disease had a higher preoperative Briganti nomogram lymph node involvement risk (14% vs. 29%, p<0.001). Logistic regression analyses revealed that preoperative Briganti’s lymph node involvement risk was significantly associated with a lower risk of false positive PSMA-PET (OR: 0.02, 95%CI 0.01-0.2, p<0.001).
Patients with a false positive PSMA-PET (miN1 - pN0) exhibited higher 2-year biochemical recurrence-free survival rates compared to miN1 - pN1 patients (54% vs. 24%, p=0.02).
Utilizing a locally weighted scatterplot smoothing (Lowess) plot, they identified a non-linear correlation between lymph node involvement risk and false positive PSMA-PET scans. They observed a decrease in the false positive rate from 60% to 10% with increasing Briganti’s LNI risk percentage.
The presenter concluded his presentation with the following key points:
- A significant portion of patients with miN1 disease on staging PSMA-PET scans, had false positive results.
- Patients with positive PSMA-PET and low lymph node involvement risk based on Briganti’s nomogram should not be denied curative-intent treatment options due to a significant risk of false positive findings in PSMA-PET staging.
Presented by: Francesco Barletta, MD, Urology resident and clinical researcher at the IRCCS Ospedale San Raffaele
Written by: Julian Chavarriaga, MD – Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @chavarriagaj on Twitter during the 2024 American Urological Association (AUA) Annual Meeting, San Antonio, TX, Fri, May 3 – Mon, May 6, 2024.