Diagnostic accuracy of bone scan at different PSA levels in biochemical recurrence of prostate cancer

Abstract

ObjectiveTo determine the diagnostic accuracy of Bone Scan at different PSA levels for detecting skeletal metastases in men with biochemical recurrence of prostate cancer. MethodsWe conducted a retrospective review of the statewide RIS-PACS to identify 251 men with biochemical recurrence who underwent both a Bone Scan and Ga68 PSMA PET/CT (within 2 months of each other) between September 2019 and December 2022 at a single institution. The Ga68 PSMA PET/CT report was considered to be the reference standard. ResultsThe median age was 72 years (IQR 67–76) with a median PSA level of 1 ng/ml (IQR 0.25–2.8). Using Ga68 PSMA PET/CT as the reference standard, 68/251 patients (25%) were positive for osseus metastases. Overall sensitivity and specificity of Bone Scan was 51% (95% CI 40–64%) and 99% (95% CI 98–100%) respectively. Using PSA banding, a PSA threshold of 20 ng/ml provided the greatest discriminatory benefit with sensitivity of the Bone Scan below the threshold being 46% (95% CI 33–59%) and above the threshold being 89% (95% CI 68–100%). Specificity remained consistently high both below and above this threshold. ConclusionBone Scan provides greater diagnostic accuracy for detecting skeletal metastases in biochemical recurrence when the PSA level is above 20 ng/ml. This knowledge is valuable in optimising imaging algorithms in biochemical recurrence, particularly in regions where PSMA PET/CT is less readily available or affordable.