(UroToday.com) The 2023 EAU annual meeting included a session on the role of imaging and PSA density for biopsy indication, and tumor staging, featuring a presentation by Dr. Paola Arena discussing a single institutional analysis of the prospective evaluation for the diagnostic accuracy of different PSMA PET/CT tracers for nodal staging of radical prostatectomy candidates. PSMA PET/CT has emerged as tool for primary and recurrent prostate cancer. The rationale of the technique is the use of agents able to detect PSMA, overexpressed in prostate cancer cells. Radiopharmaceuticals adopted are 68Ga-PSMA-11 or 18F-PSMA-1007. Despite the widespread use of PSMA PET/CT, the impact of lack of standardization and use of different tracers on its diagnostic accuracy is still unknown.
This study reviewed prospectively collected data of patients referred to a tertiary hospital from October 2020 to January 2023. Dr. Arena and colleagues included patients who underwent 68Ga-PSMA-11 or 18F-PSMA-1007 PET/CT in a primary staging setting who underwent robot-assisted radical prostatectomy with lymph node dissection:
They excluded PSMA PET/CT performed elsewhere and patients who did not receive lymph node dissection. For each examination, the maximum Standard Uptake Value (SUV) of both the primary tumor and lymph nodes, as well as the SUV node to background ratio was reported. They adopted 2 different cut off of node to background ratio (≥/< 2 vs. >/≤ 15.5) to evaluate the performance of both tracers. The first one was empirically decided, the second was based on Liu methods for optimal cut-point. The aim was to evaluate the accuracy of the two agents for nodal staging and to compare their diagnostic performance.
Overall, 156 patients were included, of which the mean age was 67 (60-71) years of age and mean PSA was 7.6 (5.66-14) ng/ml. Based on EAU risk group, 80 (51%) patients had a low/intermediate-risk and 76 (49%) had high-risk prostate cancer. Overall, 83 (53.2%) patients underwent 68Ga-PSMA-11 and 73 (46.8%) 18F-PSMA-1007 PET/CT. PSMA PET/CT showed highly suspicious lymph nodes in 19 patients, 8 with 68Ga-PSMA-11 and 11 with 18F-PSMA-1007. At pathological report, 9 patients had positive lymph nodes, 6 detected by 68Ga-PSMA-11 and 3 by 18F-PSMA-1007. Considering a SUV cut off ratio ≥ 2 the diagnostic performance of 68Ga-PSMA-11 and 18F-PSMA-1007 PET/CT respectively was:
- Sensitivity 37.5 (15.2-64.6) and 33.3 (7.5-70.1)
- Specificity 98.5 (91.7-100) and 100 (94.4-100)
- Accuracy was slightly higher for 68Ga-PSMA-11: 0.68 (0.55-0.90) vs 0.64 (0.46-0.82) for 18F-PSMA-1007 PET/CT
Increasing the cut off to >15.5 sensitivity was 31.3 (11.0-58.7) and 11.1 (0.28-48.2) while specificity was 100 (94.5-100) and 100 (92.3- 100) for both tracers respectively. Finally, the accuracy was slightly higher for 68Ga-PSMA-11 (0.65; 0.53-0.77) vs 18F-PSMA-1007 (0.57; 0.43-0.71) PET/CT.
Dr. Arena concluded her presentation discussing a single institutional analysis of the prospective evaluation for the diagnostic accuracy of different PSMA PET/CT tracers for nodal staging of radical prostatectomy candidates with the following take-home messages:
- 18F-PSMA-1007 PET/CT showed a lower sensitivity and relatively higher specificity for nodal staging compared to 68Ga-PSMA-11, irrespective of the SUV ratio used
- Further studies are warranted to provide a better risk stratification in radical prostatectomy candidates
Presented by: Paola Arena, MD, Humanitas University, Dept. of Biomedical Sciences, Pieve Emanuele, Italy
Co-Authors: Fasulo V.1, Chiarelli G.1, Frego N.1, De Carne F.1, Maffei D.1, Jandric J.1, Gelardi F.1, Garofano G.1, Saitta C.1, Mancon S.1, Sordelli F.1, Beatrici E.1, Hurle R.2, Saita A.2, Lazzeri M.2, Guazzoni G.1, Buffi N.M.1, Lughezzani G.1, Casale P.1
Affiliations: 1Humanitas University, Dept. of Biomedical Sciences, Pieve Emanuele, Italy, 2IRCCS Humanitas Research Hospital, Dept. of Urology, Rozzano, Italy
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2023 European Association of Urology (EAU) Annual Meeting, Milan, IT, Fri, Mar 10 – Mon, Mar 13, 2023.