Clinical Insignificance of [18F]psma-1007&Amp;nbsp;avid Non-specific Bone Lesions: A Retrospective Evaluation

Purpose : [ 18 F]PSMA-1007 offers advantages of low urinary tracer excretion and improved resolution for imaging prostate cancer. However, non-specific bone lesions (NSBLs), defined as mild to moderate focal bone uptake without a typical morphological correlate on CT, are a common finding 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 classifier 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 defined 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 classifier of bone metastases using ROC curve analysis. Results : No [ 18 F]PSMA-1007 avid NSBLs met criteria for a likely malignant or definitely malignant lesion after a median 15.8-month follow-up interval (11.9% definitely benign, 50.3% likely benign, and 37.7% equivocal). There were no statistically significant 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 definite prostate cancer bone metastases, the highest SUVmax value recorded was a good classifier 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 identified in the absence of definite 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 classified as equivocal or metastatic, with patient clinical risk factors, scan appearance, and potential management implications used to guide interpretation.