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

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