Abstract
BackgroundAssessing the extent of disease in newly diagnosed prostate cancer (PC) patients is crucial for tailoring an appropriate treatment approach. Prostate-specific membrane antigen (PSMA)–targeted positron emission tomography/computed tomography (PET/CT) reportedly has greater accuracy than conventional imaging for staging PC. As with any imaging modality, pitfalls and nonspecific findings do occur. The PSMA reporting and data system (PSMA-RADS) version 1.0 offers structured interpretation of PSMA-targeted studies and classifies lesions by likelihood of clinical significance. The aim of this retrospective study was to evaluate the clinical significance of equivocal bone findings on staging PSMA-targeted imaging, as defined by PSMA-RADS version 1.0, in the preoperative setting. Fifteen of 406 consecutive patients staged by PET/CT prior to radical prostatectomy had equivocal bone lesions. The scans were retrospectively scored with the PSMA-RADS version 1.0 system, blinded to disease course and follow-up data. Postoperative persistence of prostate-specific antigen levels supported by imaging and histological findings was used as the reference standard for the true significance of equivocal imaging findings.ResultsThirteen of the 15 patients had an overall PSMA-RADS score of 3B, of whom only two had true metastatic disease. The remaining patients had scores of 4 (n = 1) or 5 (n = 1), all confirmed as true positive prostate-related malignant lesions. A per-lesion analysis identified 29 bone lesions, of which 27 were scored PSMA-RADS 3B, and only three of them were true metastases. Thus, debatable lesions proved to have no clinical significance in 84.6% of cases, and only 11% of equivocal PSMA-RADS 3B bone lesions were true positive.ConclusionsIn intermediate and high-risk patients staged prior to radical prostatectomy, the majority of PSMA-RADS 3B lesions are of no clinical relevance. Bone lesions judged as being highly suspicious for metastases (PSMA-RADS 4/5) were all validated as true positives.
Highlights
Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein overexpressed on prostate cancer (PC) cells and serves for tumor-targeted imaging with positron emission tomography/computed tomography (PET/CT) [1]
It has been suggested that 18F-PSMA-1007 PET/CT has equal or even superior detectability compared to 68 Ga-PSMA-11 [25,26,27], it may be prone to more false-positive findings [28]
PSMA-targeted imaging demonstrates improved sensitivity and specificity in detecting bone metastases compared to traditional imaging modalities, such as bone scintigraphy, CT, and Magnetic resonance imaging (MRI), in patients with primary intermediate or high-risk PC, PSMA-ligand uptake can appear in other benign as well as malignant osseous lesions [19, 23]
Summary
Prostate-specific membrane antigen (PSMA) is a type II transmembrane glycoprotein overexpressed on prostate cancer (PC) cells and serves for tumor-targeted imaging with positron emission tomography/computed tomography (PET/CT) [1]. Several systems have been proposed to facilitate the interpretation of PSMA-targeted PET scans [30,31,32,33] These systems allow for better communication between nuclear physicians and referring clinicians and offer a standardized classification scheme of equivocal findings to guide further management. The PSMA reporting and data system (PSMA-RADS) version 1.0 offers structured interpretation of PSMA-targeted studies and classifies lesions by likelihood of clinical significance. The aim of this retrospective study was to evaluate the clinical significance of equivocal bone findings on staging PSMA-targeted imaging, as defined by PSMA-RADS version 1.0, in the preoperative setting. Postoperative persistence of prostate-specific antigen levels supported by imaging and histological findings was used as the reference standard for the true significance of equivocal imaging findings
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