ASCO GU 2021: A Prospective Phase II/III Study of PSMA-Targeted 18F-DCFPyL-PET/CT in Patients with Prostate Cancer (PCa) (OSPREY): A Subanalysis of Disease Staging Changes in PCa Patients with Recurrence or Metastases on Conventional Imaging

(UroToday.com) Conventional imaging modalities including computed tomography and bone scintigraphy are routinely recommended for prostate cancer staging, however, they are limited by relatively low sensitivity and moderate specificity. In contrast, PSMA-based imaging is highly promising for prostate cancer detection, with higher sensitivity, specificity, and accuracy. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) being explored in the staging of prostate cancer. Previously, at AUA 2020, the diagnostic performance, detection rate, and potential impact of 18F-DCFPyL on the staging of patients with high- risk prostate cancer was reported. In a plenary abstract presentation in the Poster Highlights Session: Prostate Cancer session at the 2021 ASCO GU Cancers Symposium, Dr. Jeremy Durack and colleagues report on the impact of 18F-DCFPyL on the staging of patients with prostate cancer recurrence or metastases on conventional imaging.

The authors included 117 men with radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. 18F-DCFPyL-PET/CT was performed using a single dose of 9 mCi (333 MBq) of 18F-DCFPyL, administered via intravenous injection, and followed by PET/CT acquisition 1 to 2 hours thereafter. 18F-DCFPyL-PET/CT detection rates including lesion counts were systematically analyzed according to TNM staging: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b), and other visceral organs/soft tissue (M1c) with three central, blinded, and independent readers evaluating the 18F-DCFPyL scans.

The authors included 82 (70%) patients who had baseline radiographic M1 stage disease (14 patients with M1a, 50 patients with M1b, 18 patients with M1c), and 33 (28%) patients who had M0 disease based on conventional imaging (with central review), and two patients were unevaluable.

In patients with M0 disease based on conventional imaging, 18F-DCFPyL-PET/CT up-staged 19 of 33 patients (58%) to M1 disease, of whom 91% (10/11) who underwent an extra-pelvic biopsy were confirmed to have M1 disease by pathology, including 9 patients with M1b and 1 patient with M1a.

In patients with M1 disease based on conventional imaging, 18F-DCFPyL-PET/CT upstaged 10 of 64 (16%) and down-staged 18 of 82 (22%) to M0 disease. Among those who were upstaged, 4 patients were upstaged from M1a to M1b/c disease and 6 patients were upstaged from M1b to M1c disease.

On the basis of these data, the authors conclude that 18F-DCFPyL-PET/CT may be a useful tool in staging men with both metastatic and nonmetastatic relapsed prostate cancer.

Presented by: Jeremy C. Durack, MD, MS, Interventional Radiologist, Memorial Sloan Kettering Cancer Center

Written by: Christopher J.D. Wallis, Urologic Oncology Fellow, Vanderbilt University Medical Center Contact: @WallisCJD on Twitter during the 2021 ASCO Genitourinary Cancers Symposium (ASCO GU), February 11th to 13th, 2021

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