Abstract
The novel Gallium-68 prostate-specific membrane antigen (PSMA)-bis [2-hydroxy-5-(carboxyethyl)benzyl] ethylenediamine-diacetic acid positron emission tomography (PET) tracer is increasingly used in the evaluation of prostate cancer, particularly in the detection of recurrent disease. However, PSMA is expressed in nonprostatic tissues, as well as in other pathologic conditions. Here we illustrate such interpretive pitfalls with relevant images that one may encounter while reporting PSMA PET/CT. This study aims to show variation in physiological distribution of PSMA activity and uptake in various benign and neoplastic disorders that may be misinterpreted as prostatic metastatic disease. These pitfalls are illustrated to enhance awareness, aiding a more accurate interpretation of the study. Retrospective database of all (68)Ga PSMA PET/CT was created and reviewed. In total, 1115 PSMA PET/CT studies performed between February 27, 2015, and May 31, 2017, were reviewed. Any unusual uptake of PSMA was documented, described, and followed up. All cases were then subdivided into the following 4 categories: physiological uptake, benign pathological uptake, nonprostatic neoplastic uptake, and miscellaneous uptake. A variety of nonprostatic tissues and lesions, including accessory salivary gland, celiac ganglion, gall bladder, Paget's bone disease, reactive lymph nodes, non–small cell lung cancer, renal cell cancer, and neuroendocrine tumor, were found to show PSMA uptake. PSMA uptake is not prostate-specific and can be taken up physiologically and pathologically in nonprostatic tissue. It is important for reporting physicians to recognize these findings and instigate appropriate investigations when required while avoiding unnecessary procedures in physiological variation.
Highlights
Morphological imaging methods exhibit considerable limitations: sensitivity ranges between 25% and 54% for detection of local recurrence of prostate cancer by transrectal ultrasonography or computed tomography (CT) and is moderately improved using functional magnetic resonance (MR) imaging techniques [1,2,3]
Gallium-68 prostate-specific membrane antigen (PSMA)bis [2-hydroxy-5-(carboxyethyl)benzyl] ethylenediamine-diacetic acid (HBED-CC) is a relatively new positron emission tomography (PET) tracer that is increasingly used in the detection of prostatic metastases at staging and in the evaluation of recurrent disease [4,5,6,7,8]
Imaging with Gallium-68 PSMA-bis-HBED-CC is based on the fact that it binds to PSMA on the cell membrane of prostatic tumor cells
Summary
Morphological imaging methods exhibit considerable limitations: sensitivity ranges between 25% and 54% for detection of local recurrence of prostate cancer by transrectal ultrasonography or computed tomography (CT) and is moderately improved using functional magnetic resonance (MR) imaging techniques [1,2,3]. Gallium-68 prostate-specific membrane antigen (PSMA)bis [2-hydroxy-5-(carboxyethyl)benzyl] ethylenediamine-diacetic acid (HBED-CC) is a relatively new positron emission tomography (PET) tracer that is increasingly used in the detection of prostatic metastases at staging and in the evaluation of recurrent disease [4,5,6,7,8]. Studies suggest that 68-PSMA-ligand PET/CT is fairly sensitive and highly specific in the detection of prostatic metastases even at low prostate-specific antigen levels [7, 9, 10]. It has been shown that various normal nonprostatic tissues express PSMA and show PSMA tracer avidity. Some of the PSMA-avid nonprostatic malignancies have been shown to express PSMA on their cell or in their neovascularity and could be confused with prostatic metastases. The purpose of this review is to illustrate such interpretive pitfalls that one may encounter during reporting by a process of literature review and integrating some of our cases as examples to help avoid misdiagnosis and mismanagement
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