Abstract
Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) imaging is an emerging technique for evaluating patients with prostate cancer (PCa) in a variety of clinical contexts. As with any new imaging modality, there are interpretive pitfalls that are beginning to be recognized. In this report, we describe the findings in a 63-year-old male with biochemically recurrent PCa after radical prostatectomy who was imaged with 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid ([18F]DCFPyL), a small-molecule inhibitor of PSMA. Diffuse radiotracer uptake was noted throughout the sacrum, corresponding to imaging findings on contrast-enhanced computed tomography (CT), bone scan, and pelvic magnetic resonance imaging consistent with Paget's disease of bone. The uptake of [18F]DCFPyL in Paget's disease most likely results from hyperemia and increased radiotracer delivery. In light of the overlap in patients affected by PCa and Paget's disease, it is important for nuclear medicine physicians and radiologists to be aware of the potential for this diagnostic pitfall when interpreting PSMA PET/CT scans. Correlating findings on conventional imaging such as diagnostic CT and bone scan can help confirm the diagnosis.
Highlights
Limitations in conventional imaging for evaluating prostate cancer (PCa) have spurred the development of several new positron emission tomography (PET) molecular imaging agents
In this report we describe the uptake of the prostate-specific membrane antigen (PSMA)-targeted radiotracer 2-(3-{1-carboxy-5-[(6-[18F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid ([18F]DCFPyL) [3] in Paget’s disease of bone, a common condition in the same elderly male population that is at risk for PCa
Given the immense volume of data that has been generated on the use of PSMA-targeted radiotracers for PCa PET imaging, it is almost certain that this modality will continue to be used extensively in imaging trials and may become a part of the clinical imaging workup of patients with PCa
Summary
Limitations in conventional imaging for evaluating prostate cancer (PCa) have spurred the development of several new positron emission tomography (PET) molecular imaging agents. Among the most extensively studied radiotracers are smallmolecule inhibitors of prostate-specific membrane antigen (PSMA) [1,2,3], a transmembrane enzyme that is highly expressed in PCa and the expression of which is positively correlated with aggressive features of the disease [4,5,6] These small-molecule imaging agents have demonstrated several important findings in early clinical studies of PCa patients, including [1] the reliable identification of clinically significant disease in preprostatectomy patients [7], [2] greater sensitivity for identifying sites of disease in patients with metastatic PCa compared with conventional imaging with contrastenhanced computed tomography (CECT) and [99mTc]methylene diphosphonate (MDP) bone scan (BS) [8], and [3] higher sensitivity than conventional imaging for detecting lesions in patients with biochemical recurrence after prostatectomy [9]. In light of the propensity for PCa to metastasize to bone, potential false-positive bone lesions could significantly confound the interpretation of PSMA PET scans
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