Bisphosphonate Bone Imaging Agent [68Ga]Ga-P15-041 for Evaluating Skeletal Metastases in Prostate Cancer: A Comparison With [68Ga]Ga-PSMA-11 PET/CT.

[BACKGROUND] Accurate diagnosis of bone metastases in prostate cancer is essential for staging, prognosis, and treatment. Although PSMA PET/CT is highly effective, complementary imaging is needed to clarify indeterminate lesions. The novel bisphosphonate-based agent [68Ga]Ga-P15-041 shows superior diagnostic accuracy over conventional SPECT imaging, indicating its potential as an auxiliary diagnostic tool. This study explores its role in detecting and assessing prostate cancer bone metastases.

[PATIENTS AND METHODS] This prospective study enrolled 35 patients with prostate cancer and skeletal metastases, who underwent both [68Ga]Ga-P15-041 and [68Ga]Ga-PSMA-11 PET/CT within 1 week. Lesions detected by [68Ga]Ga-PSMA-11 PET/CT were classified using Prostate-specific Membrane Antigen Reporting and Data System 2.0.

[RESULTS] [68Ga]Ga-P15-041 PET/CT detected more lesions than [68Ga]Ga-PSMA-11 PET/CT (525 vs 509, P < 0.001) and demonstrated significantly higher tracer uptake, with a mean SUV of 20.73 ± 14.67 compared with 11.13 ± 8.12 (P < 0.0001). It detected significantly more osteoblastic lesions (504 vs 391, P < 0.0001). In addition, this study established the Reporting and Data System for [68Ga]Ga-P15-041 (P15-041-RADS), which classifies prostate cancer bone metastases into 5 categories based on SUVmax and morphologic changes. P15-041-RADS reclassified 85.71% of Prostate-specific Membrane Antigen Reporting and Data System category 3 lesions and 95.00% of 5T lesions into higher-confidence categories, offering improved diagnostic clarity. Limitations include small sample size and lack of pathologic gold standards.

[CONCLUSIONS] [68Ga]Ga-P15-041 PET/CT is a promising and accessible bone imaging agent that could complement [68Ga]Ga-PSMA-11 PET/CT in the diagnosis and classification of bone metastases in prostate cancer.