Clinical insignificance of [18F]PSMA-1007 avid non-specific bone lesions: a retrospective evaluation

Abstract

Purpose: [ 18 F]PSMA-1007 offers advantages of low urinary tracer excretion and improved resolution for imaging prostate cancer. However, non-speci c bone lesions (NSBLs), de ned as mild to moderate focal bone uptake without a typical morphological correlate on CT, are a common nding on [ 18 F]PSMA-1007 PET/CT. The purpose of this study was to investigate the clinical outcomes of patients with [ 18 F]PSMA-1007 avid NSBLs, to determine whether patients with NSBLs represent a higher risk clinical cohort, and to determine whether SUVmax can be used as a classi er of bone metastasis.Methods: A retrospective audit of 214 men with prostate cancer was performed to investigate the clinical outcomes of [ 18 F]PSMA-1007 avid NSBLs according to de ned criteria. We also compared the serum PSA, Gleason score and uptake time of patients with [ 18 F]PSMA-1007 avid NSBLs to patients without [ 18 F]PSMA-1007 avid bone lesions. Finally, we assessed whether SUVmax is a good classi er of bone metastases using ROC curve analysis.Results: No [ 18 F]PSMA-1007 avid NSBLs met criteria for a likely malignant or de nitely malignant lesion after a median 15.8-month follow-up interval (11.9% de nitely benign, 50.3% likely benign, and 37.7% equivocal). There were no statistically signi cant differences in serum PSA, Gleason score and uptake time between patients with [ 18 F]PSMA-1007 avid NSBLs and those without [ 18 F]PSMA-1007 avid bone lesions. All NSBLs with adequate follow-up had SUVmax ≤11.1. When comparing NSBLs to de nite prostate cancer bone metastases, the highest SUVmax value recorded was a good classi er of bone metastasis, and an SUVmax cut-point of ≥7.2 maximised the Youden's index.Conclusion: [ 18 F]PSMA-1007 avid NSBLs rarely represent prostate cancer bone metastases. When identi ed in the absence of de nite metastatic disease elsewhere, it is appropriate to classify those with SUVmax <7.2 as likely benign. NSBLs with SUVmax 7.2-11.1 may be classi ed as equivocal or metastatic, with patient clinical risk factors, scan appearance, and potential management implications used to guide interpretation.

Risk of metastatic disease using [18F]PSMA-1007 PET/CT for primary prostate cancer staging

“…Thirdly, a common issue with the [ 18 F]PSMA-1007 radiotracer is focal uptake in non-specific bone lesions (NSBLs) without an underlying CT correlate definite for prostate metastasis. Recent data suggest that these NSBLs rarely represent metastatic lesions, supporting our image interpretation that equivocal lesions are not considered malignant [ 36 ]. Lastly, a small number of patients were on ADT before the PET/CT scan during initial staging, presumably due to high-risk features, potentially influencing the PSMA targeted PET/CT results [ 37 ].…”

18F-PSMA-1007 PET in Biochemical Recurrent Prostate Cancer: An Updated Meta-Analysis

“…These findings underline that the main advantage of 18 F-PSMA-1007 compared to other PSMA-targeted PET tracers is its reduced urinary clearance allowing an excellent assessment of the pelvic region owing to the reduced interference of the urinary radioactivity [ 15 , 16 ]. On the other hand, focal unspecific bone uptake on 18 F-PSMA-1007 PET seems a frequent finding (more frequent on digital PET scanners than analog PET scanners), and it should be interpreted carefully to avoid PCa overstaging [ 39 , 40 ].…”

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

“…Moreover, the number of reports of invasive measures to clarify UBL, including rib resection [14,15], suggest that occasionally, diagnostic dilemmas can occur which warrant highly invasive measures and are a clinically relevant issue. Although SUV cut-off values have been advanced as a means of differentiating between benign and malignant lesions [4], we nd in our series of biopsies a substantial overlap between lesions judged to be clinically at high risk and with high tracer avidity, yet with benign histology. Moreover, Grünig et al nd that even with follow up, 43% of UBL remain unclear, further demonstrating that there is currently no satisfactory method to differentiate reliably between UBL in [ 18 F]PSMA-1007 PET/CT [5].…”

“…Amongst these tracers is [ 18 F]PSMA-1007, for which previous studies suggest a higher PET-positivity rate [3]. However, there are a number of reports of high rates (in up to half of all patients) of unspeci c or equivocal bone lesions (UBL), which cannot be clearly classi ed as benign or malignant [4,5]. These can often pose diagnostic conundrums and place the patient at risk of being incorrectly staged; this could adversely impact treatment outcomes or might require further diagnostic work-up [6].…”