18F-PFPN PET: A New and Attractive Imaging Modality for Patients with Malignant Melanoma

18F-FDG PET has limited diagnostic applications in malignant mela-noma (MM). 18F-N-(2-(diethylamino)ethyl)-5-(2-(2-(2-fluoroethoxy) ethoxy)ethoxy)picolinamide (18F-PFPN) is a novel PET probe with high affinity and selectivity for melanin. We conducted a clinical study with 2 aims, first to investigate the biodistribution and radiation dosimetry of 18F-PFPN in healthy volunteers, and second, to examine the diagnostic utility of 18F-PFPN PET imaging in patients with MM. Methods: 18F-PFPN was synthesized through a fluoro-for-tosyl exchange reaction. Five healthy volunteers were enrolled to investi-gate the biodistribution, pharmacokinetics, radiation dosimetry, and safety of the tracer. Subsequently, a total of 21 patients with clinically suspected or confirmed MM underwent both 18F-PFPN PET/MRI and 18F-FDG PET/CT scans. The normalized SUVmax of selected lesions was determined for both tracers and compared in patient-and lesion -based analyses. Results: 18F-PFPN has an elevated radiochemical yield and was highly stable in vivo. In healthy volunteers, 18F-PFPN was safe and well tolerated, and its effective absorbed dose was comparable to that of 18F-FDG. In patient-based analysis, 18F-PFPN uptake was higher than 18F-FDG for both primary tumors and nodal metastases. In lesion-based analysis,18F-PFPN PET imaging could detect 365 metastases that were missed on 18F-FDG PET. Addition-ally, 18F-PFPN PET imaging had clinical value in distinguishing false -positive lesions on 18F-FDG PET. Conclusion: 18F-PFPN is a safe and well-tolerated melanin PET tracer. In a pilot clinical study, 18F-PFPN PET imaging outperformed traditional 18F-FDG PET in identify-ing both primary MM and its distant spread.

Automated summary

18F-PFPN is a novel PET probe with high affinity and selectivity for melanin, showing elevated radiochemical yield and stability in vivo. In clinical studies, it outperformed traditional 18F-FDG PET in identifying primary MM and its distant spread, demonstrating higher uptake and ability to detect more metastases. Additionally, it showed clinical value in distinguishing false-positive lesions on 18F-FDG PET.