Prospective Comparison of PET Imaging with PSMA-targeted ¹⁸F-DCFPyL versus Na¹⁸F for Bone Lesion Detection in Patients with Metastatic Prostate Cancer

Abstract

Purpose: Bone metastases in prostate cancer (PCa) have important prognostic significance and imaging modalities used for PCa staging should have high sensitivity for detecting such lesions. Prostate-specific membrane antigen (PSMA)-targeted positron emission tomography (PET) radiotracers are promising new agents for imaging PCa. We undertook a head-to-head comparison of PSMA-targeted ¹⁸F-DCFPyL PET to Na¹⁸F PET to determine which modality was more sensitive for the detection of lesions suspicious for bone metastases in a group of patients with metastatic PCa. Materials and Methods: Patients with progressive, metastatic PCa were prospectively imaged with both ¹⁸F-DCFPyL and Na¹⁸F PET/CT, with both scans occurring within 24 hours of each other. A consensus, 2-reader central review was carried out to identify all bone lesions suspicious for sites of PCa involvement on both scans and maximized standardized uptake values corrected for weight (SUV_max) and lean body mass (SULmax) were recorded. Soft tissue lesions were also noted on both scans and SUV_max, SULmax, and PSMA-RADS version 1.0 scores were recorded. Data from the two scans was compared using a generalized estimating equation. Results: In total, 16 patients meeting all inclusion criteria were enrolled in this study and 15/16 (93.8%) were imaged with both PET radiotracers. A total of 405 bone lesions suspicious for sites of PCa were identified on at least one scan. On ¹⁸F-DCFPyL PET/CT, 391 (96.5%) were definitively positive, 4 (1.0%) were equivocally positive, and 10 (2.5%) were negative. On Na¹⁸F PETCT, the corresponding values were 388 (95.8%), 4 (1.0%), and 13 (3.2%). Of the definitively negative lesions on ¹⁸F-DCFPyL PET, 8/10 (80.0%) were sclerotic and 2/10 (20.0%) were infiltrative/marrow-based. Additionally, 12/13 (92.3%) of the definitively negative lesions on Na¹⁸F PET were infiltrative/marrow-based and 1/13 (7.7%) was lytic. 78 PSMA-RADS-4, 17 PSMA-RADS-5, and 1 PSMA-RADS-3C soft tissue lesions were also identified. Conclusion: PET/CT imaging using ¹⁸F-DCFPyL and Na¹⁸F PET had nearly identical sensitivities for the detection of bone lesions in patients with metastatic PCa. As would be expected, PSMA-targeted PET provides more information on soft tissue disease. There may be little additional value to imaging patients with PCa with Na¹⁸F after a PSMA-targeted PET scan has already been performed.