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

Abstract

The purpose of this study was to compare the diagnostic performance of ¹⁸F-DCFBC PET/CT, a first-generation ¹⁸F-labeled 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. <b>Methods:</b> Twenty-eight prostate cancer patients with metastatic disease on conventional imaging prospectively received up to 4 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 a median follow-up interval of 5.7 mo (range, 4.2-12.6 mo). Lesion detection was compared across the 2 PET/CT agents at each time point. Detection and 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 nonparametric statistical testing (Spearman correlation, Wilcoxon rank). <b>Results:</b> Twenty-six patients had metastatic disease detected on ¹⁸F-NaF or ¹⁸F-DCFBC at baseline, and 2 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 or ¹⁸F-DCFBC. ¹⁸F-NaF detected significantly more bone lesions than ¹⁸F-DCFBC (<i>P</i> < 0.001). Correlation of PSA with patient-level SUV metrics was strong in ¹⁸F-DCFBC (ρ > 0.5, <i>P</i> < 0.01) and poor in ¹⁸F-NaF (ρ < 0.3, <i>P</i> > 0.1). When PSA levels were combined with treatment status, patients with below-median levels of PSA (<2 ng/mL) on androgen deprivation therapy (<i>n</i> = 11) demonstrated more lesions on ¹⁸F-NaF than ¹⁸F-DCFBC (<i>P</i> = 0.02). In PSA greater than 2 ng/mL, patients on androgen deprivation therapy (<i>n</i> = 8) showed equal to or more lesions on ¹⁸F-DCFBC than on ¹⁸F-NaF. <b>Conclusion:</b> The utility of PSMA-targeting imaging in metastatic prostate cancer appears to depend on patient disease course and treatment status. Compared with 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 NaF PET/CT.