A prospective phase II/III multicenter study of PSMA-targeted 18F-DCFPyL PET/CT imaging in patients with prostate cancer (OSPREY): A sub-analysis of regional and distant metastases detection rates at initial staging by 18F-DCFPyL PET/CT.

Abstract

9 Background: Current imaging modalities are suboptimal for the initial staging of men at risk of harboring occult metastatic prostate cancer (PCa). PSMA-based imaging is considered highly promising for PCa detection. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) that may be useful in staging of pts with high risk PCa. The diagnostic performance of 18F-DCFPyL regarding regional and distant metastases has been previously reported. Here we report on detection rates and the resulting impact 18F-DCFPyL may have on staging of pts with high risk PCa. Methods: 18F-DCFPyL PET/CT was evaluated in 252 men with high-risk PCa who were planned for radical prostatectomy with lymphadenectomy (RP-PLND). 9 mCi (333 MBq) of 18F-DCFPyL was administered 1-2 hours prior to PET/CT. Based on TNM staging, 18F-DCFPyL PET/CT detection rates including lesion counts were systematically analyzed: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b) & other visceral organs/soft tissue (M1c). Three central, blinded, and independent readers evaluated the 18F-DCFPyL scans. Results: At study entry, 97% and 99% of all evaluable pts had no known nodal or metastatic disease, respectively, based on standard cross-sectional imaging. Of these, 18F-DCFPyL PET/CT staged 37 (14.7%) pts with N1 disease and 27 (10.7%) pts with M1 disease (1 [0.4%] M1a, 23 [9.1%] M1b, and 3 [1.2%] M1c). In total, 56 (22%) of patients were upstaged to N1 or M1 disease by 18F-DCFPyL. The positive predictive value of 18F-DCFPyL based on histopathologic validation for pelvic LNs was 86.7% (95% CI: 70, 95). Only one patient in Cohort A underwent a biopsy of their 18F-DCFPyL detected M1 finding; histopathology confirmed the metastatic lesion in the spine to be a true positive. Conclusions: A total of 22% of pts with high-risk PCa planned for RP-PLND had regional or distant metastatic lesions detected on 18F-DCFPyL PET/CT. These results suggest the potential utility of 18F-DCFPyL PET/CT in the staging of men with newly diagnosed high risk PCa to develop optimized treatment paradigms. Clinical trial information: NCT02981368.