A Prospective Comparison of 18F-Sodium Fluoride PET/CT and PSMA-Targeted 18F-DCFBC PET/CT in Metastatic Prostate Cancer

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Abstract
Purpose: The purpose of this study was to compare the diagnostic performance of 18F-DCFBC positron emission tomography/computed tomography (PET/CT), a first generation 18F-labelled prostate-specific membrane antigen (PSMA)-targeted agent, and 18F-NaF PET/CT, a sensitive marker of osteoblastic activity, in a prospective cohort of patients with metastatic prostate cancer. Methods: Twenty-eight prostate cancer patients with metastatic disease on conventional imaging prospectively received up to four PET/CT scans. All patients completed baseline 18F-DCFBC PET/CT and 18F-NaF PET/CT scans and 23 patients completed follow-up imaging, with median follow-up interval of 5.7 months (range 4.2-12.6 months). Lesion detection was compared across the two PET/CT agents at each timepoint. Detection and standardized uptake value (SUV) characteristics of each PET/CT agent were compared with serum prostate-specific antigen (PSA) levels and treatment status at the time of baseline imaging using non-parametric statistical testing (Spearman correlation, Wilcoxon rank). Results: Twenty-six patients had metastatic disease detected on 18F-NaF or 18F-DCFBC at baseline and two patients were negative on both scans. Three patients demonstrated soft-tissue only disease. Of 241 lesions detected at baseline, 56 were soft-tissue lesions identified by 18F-DCFBC only and 185 bone lesions detected on 18F-NaF and/or 18F-DCFBC. 18F-NaF detected significantly more bone lesions compared to 18F-DCFBC (p0.5, p18F-NaF (ρ0.1). Combining PSA levels with treatment status, patients with below median levels of PSA (2ng/ml, patients on ADT (N = 8) showed equal or more lesions on 18F-DCFBC compared to 18F-NaF. Conclusion: The utility of PSMA-targeting imaging in metastatic prostate cancer appears to depend on patient disease course and treatment status. Compared to 18F-NaF PET/CT, 18F-DCFBC PET/CT detected significantly fewer bone lesions in the setting of early or metastatic castrate sensitive disease on treatment. However, in advanced metastatic castrate-resistant prostate cancer, 18F-DCFBC PET/CT shows good concordance with 18F-NaF PET/CT.

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