SUO 2017: 68 GA-PSMA PET/CT Versus MP-MRI For Locoregional Prostate Cancer Staging: Correlation With Final Histopathology

Washington, DC ( Introduction: It is well known that prostate-specific membrane antigen (PSMA) positron emission tomography (PET) can be used to locate lesions based on PSMA avidity. However guidelines on its use are limited by its infancy. The authors aimed to compare multiparametric magnetic resonance imaging (mpMRI) and PSMA PET/CT to radical prostatectomy histopathology.

Methods: This was a retrospective study from February 2015 to January 2017 of 50 patients staged using PSMA PET/CT and mpMRI, who then underwent radical prostatectomy. Pre-operative PSMA PET/CT and mpMRI were paired with their corresponding histological tumor.

Results: A total of 81 lesions were identified by histopathology. Fifty index lesions were detected across the three modalities: 50 by histopathology (gold standard), 50 by PSMA PET/CT, and 47 by mpMRI. Thirty-four intra-prostatic secondary lesions were detected: 31 by histopathology, 31 by PSMA PET/CT, and 17 by mpMRI. PSMA had better sensitivity for index lesion localization than mpMRI (81.1% vs. 64.6%). mpMRI failed to detect 18 histology-confirmed lesions (3 index, 15 secondary) in 16 patients. Specificity for mpMRI and PSMA PET/CT was similar (84.6% vs. 82.7%). SUVmax of index lesions ranged from 2.9 to 39.6 (M=9.27 ± 6.41). There was good differentiation between background SUV and lesion SUVmax (R=0.24, p=0.09). Index
lesion SUVmax was positively correlated with PSA (R=0.41, p=0.004) and ISUP grade (R=0.48, p<0.001).

Conclusion: PSMA-PET/CT provided superior detection of prostate cancer lesions with better sensitivity than mpMRI. PSMAPET/CT can be used to enhance locoregional mpMRI to provide improved detection and characterization of lesions.

Speaker: Matthew Winter, USC California, USA

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, @GoldbergHanan, at the 18th Annual Meeting of the Society of Urologic Oncology, November 29-December 1, 2017 – Washington, DC