(UroToday.com) The 2023 European Association of Urology (EAU) annual congress held in Milan, Italy between March 10th and 13th, 2023 was host to a prostate cancer abstract session on the role of imaging and PSA density for biopsy indication and tumor staging. Dr. Alexey Aksenov presented the results of his group’s study evaluating 68Ga and 18F–PSMA PET/CT for primary diagnosis before radical prostatectomy.
Dr. Aksenov began by highlighting that PSMA-PET/CT has been demonstrated to have excellent performance characteristics for detecting regional nodal involvement and metastatic disease in both the pre-operative1 and biochemical recurrence settings.2 The role of PSMA-PET/CT in the primary diagnosis of intraprostatic tumors remains limited due to the emergence/implementation of multiparametric MRIs. Previous studies have shown that 18F-labelled, compared to 68Ga-labelled, PSMA ligands may have a potential advantage for pelvic imaging purposes due to minimal urinary excretion. The objective of this study was to compare PSMA-PET/CT to mpMRI for the primary diagnosis of intraprostatic cancer and to compare the two different radiopharmaceuticals in this setting.
Between January 2020 and May 2022, 459 robotic-assisted and 41 open radical prostatectomies with extended pelvic lymph node dissections were performed. Of these 500 patients, 77 (15%) had a PSMA-PET/CT performed for primary pre-operative diagnostic purposes, of which 41 (53%) and 36 (47%) were using 68Ga (Group 1) and 18F (Group 2) labelled radiotracers, respectively. Of these 77 patients, 56 (73%) underwent a concurrent mpMRI preoperatively. Using this cohort, the authors conducted a retrospective analysis of the PSMA-PET/CT and mpMRI data with regards to the detection of primary and secondary prostate lesions. The radical prostatectomy specimen was considered as the reference standard.
The mean patient age was 67 years (range: 49 to 81 years) and mean prostate volume 48 cm3 (range: 10 to 183 cm3). Among the 77 patients, 42 (55%) had high-risk, 34 (44%) had intermediate-risk, and one (1.3%) had low-risk disease, defined as per the NCCN risk stratification. The median PSA levels were 16.4 and 27.1 ng/ml in groups 1 and 2, respectively. A robotic radical prostatectomy was performed in 71/77 patients, with the remaining having an open approach.
There were no significant differences between the two groups with respect to detection of the primary prostate lesion:
- Group 1 (68Ga): sensitivity of 95.1%
- Group 2 (18F): sensitivity of 91.4%
The sensitivity of PSMA-PET/CT for detection of secondary prostate lesions was superior in the 18F group:
- Group 1 (68Ga): Sensitivity of 67.5%
- Group 2 (18F): Sensitivity of 83.3%
Conversely, the sensitivity of mpMRI for the detected of the primary prostate lesion was 98.2%, but only 36.4% for the detection of secondary lesions, and this was inferior to the sensitivities observed with either PSMA-based tracer.
The investigators concluded that PSMA-PET/CT showed no superiority, compared to mpMRI, for the detection of primary prostate lesions. However, PSMA-PET/CT, irrespective of tracer used, was superior for the detection of secondary prostate lesions. This was particularly notable for 18F-radiolabelled PSMA-PET/CTs which had a sensitivity of 83.3% for detection of secondary lesions (68% for 68Ga and 36% for mpMRI). The authors hypothesized that the combination of a PSMA-PET/CT and mpMRI could improve the sensitivity of primary prostate cancer detection and help minimize unnecessary repeat prostate biopsies. The preferential application of 18F-PSMA ligand compared with 68Ga-PSMA ligand could be favored within the context of a PSMA-guided fusion biopsy in select cases and when planning a nerve-sparing procedure or focal therapies.
Presented by: Alexey Aksenov, MD, City Hospital Karlsruhe, Department of Urology, Karlsruhe, Germany,
Written by: Rashid K. Sayyid, MD, MSc – Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @rksayyid on Twitter during the 2023 European Association of Urology (EAU) Annual Meeting, Milan, IT, Fri, Mar 10 – Mon, Mar 13, 2023.
References:1. Hofman MS, et al. Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA): a prospective, randomised, multicentre study. Lancet 2020;395(10231):1208-1216.