(UroToday.com) The 2023 SNMMI annual meeting included a prostate cancer session, featuring a presentation by Dr. Jie Zang discussing the comparison of 18F-Thretide PET/CT and multiparametric MRI for the detection of intermediate‐ and high‐risk prostate cancer. Previous studies have shown that 18F-Thretide has good in vivo and in vitro stability and can accumulate specifically in PSMA-expressing tumors with high binding affinity, good safety, and good selectivity, which results in increased diagnostic confidence.1 The main objective of this prospective study presented by Dr. Zang and colleagues at the SNMMI 2023 annual meeting was to assess the value of 18F-Thretide (targeting PSMA) PET/CT imaging in patients with intermediate‐ and high‐risk prostate cancer before planned curative‐intent radical prostatectomy and pelvic lymph node dissection, and to compare the 18F-Thretide PET/CT PET/CT findings with standard of care pelvic multi‐parametric magnetic resonance imaging (mpMRI), bone scintigraphy and histopathology.
A total of 45 patients (mean age: 69.4 years, baseline mean trigger PSA 23.5 ± 28.0 ng/mL) with biopsy proven prostate cancer were enrolled in this prospective study. All patients underwent 18F-Thretide PET/CT, MRI and bone scintigraphy; any drug-related side effects were recorded and the vital parameters of the patients were observed for one week. The mpMRI images were scored with the PI-RADS version 2.1 and were classified as either negative (PI-RADS 1–3) or positive (PI-RADS 4–5). PET/CT imaging and bone scintigraphy was independently evaluated and the presence of suspicious lesions was reported by two double-trained board-certified nuclear medicine physicians who were blinded to the mpMRI and pathological results. 18F-Thretide PET/CT findings were correlated with the results of mpMRI and histopathology; a consensus of imaging, clinical and/or follow‐up findings were used to determine the distant metastases, which were not verified by histopathology.
All patients tolerated the 18F-Thretide PET/CT well, and vital parameters remained stable with no patients reporting any new symptoms during the observation period. Overall, a total of 38 of 45 patients underwent curative‐intent radical prostatectomy and pelvic lymph node dissection.
Of the 45 patients, 37 (82.2%) patients presented with a pathologic mpMRI, and 44 (97.8%) with a pathologic 18F-Thretide PET/CT (p = 0.030). The SUVmax of the primary tumors upon 18F-Thretide PET/CT was 18.7 ± 20.5. There was a low but significant correlation between SUVmax and baseline trigger PSA (r = 0.371, p = 0.014):
But no correlation between SUVmax and risk stratification (p = 0.294). The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of 18F-Thretide PET/CT in diagnosing pelvic lymph node metastasis were 60.0%, 98.7%, 97.6%, 64.3%, and 98.7%, respectively. Additionally, the number of lesions displayed on bone scintigraphy were less than those on 18F-Thretide PET/CT:
Immunohistochemical results showed that the SUVmax quantified from 18F-Thretide PET/CT was correlated with PSMA expression level (r = 0.529, p = 0.001):
Dr. Zang concluded this presentation discussing the comparison of 18F-Thretide PET/CT and multiparametric MRI for the detection of intermediate‐ and high‐risk prostate cancer with the following take-home messages:
- 18F-Thretide PET/CT shows high diagnostic performance for patients with intermediate‐ and high‐risk prostate cancer and is superior to mpMRI and bone scintigraphy
- There is a significant correlation between SUVmax of 18F-Thretide PET/CT and baseline trigger PSA
Presented by: Jie Zang, Fujian Medical University, Fuzhou, China
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2023 Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting, Chicago, IL, Sat, June 24 – Tues, June 27, 2023.
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