The significance of equivocal bone findings in staging PSMA imaging in the preoperative setting: validation of the PSMA-RADS version 1.0

Abstract

Background Assessing 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. Results Thirteen 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. Conclusions In 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.

Assessment of Malignancy and PSMA-expression of Uncertain Bone Lesions in [18F]PSMA-1007 PET/CT for Prostate Cancer- a Single Centre Experience of PET-guided Biopsies

“…We found that only one out of eleven lesions biopsied was a metastasis of PC. Similar results were reported in a series of bone lesions with follow-up, albeit in a small cohort of patients (n=15) with primary PC [10]. Nevertheless, we interpret these studies with small cohorts with caution; larger and better-powered studies are required to estimate the true scale of the problem.…”

“…The available literature seldom reports any comparative imaging data or uses a reference standard to con rm equivocal PET-ndings [3], and thus represents an urgently unmet need in evidence-based imaging for PC. Although follow-up data for a small cohort of patients with UBL in primary PC are reported [10], no similar data with a histopathological reference standard has been published for UBL in a biochemically recurrent setting, where histological con rmation is less readily available. PET-guided biopsies are a useful and minimally invasive method of obtaining material for biopsy, particularly where in the absence of morphological ndings in the CT, conventional CT-guided biopsy cannot be performed [11].…”

Intraindividual comparison of [68 Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 in prostate cancer patients: a retrospective single-center analysis

“…Multifocal low-intensity bone uptake, especially in the ribs, without correlation in morphologic imaging, was the most common manifestation of unspecific uptake in [ 18 F]-F-PSMA-1007 PET. This pattern is well known [ 16 , 25 , 32 ], although it has not yet been fully explained, and rarely represents a diagnostic challenge in many cases. Recently, Arnfield et al suggested an SUV max threshold of 7.2 under which these lesions could be interpreted as likely benign [ 33 ].…”

Comparing the clinical performance and cost efficacy of [68Ga]Ga-PSMA-11 and [18F]PSMA-1007 in the diagnosis of recurrent prostate cancer: a Markov chain decision analysis

“…For example, a number of reports describe increased non-specific radioligand uptake with [ 18 F]PSMA-1007 compared to [ 68 Ga]Ga-PSMA-11 [8]. Indeed, Kuten et al find that 13/15 (87%) patients undergoing [ 18 F]PSMA-1007 PET/CT (albeit in primary PC) had equivocal bone lesions, of which a sizeable minority (11%) were TP findings [38]. These studies lend support to our observation that the rate of indeterminate findings was significantly higher for [ 18 F]PSMA-1007 compared to [ 68 Ga] Ga-PSMA-11 (17.2% vs. 8.2%, p = 0.02).…”