A Novel Melanin-Targeted F-PFPN Positron Emission Tomography Imaging for Diagnosing Ocular and Orbital Melanoma

Objective: F-N-(2-(Diethylamino)ethyl)-5-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy) picolinamide (F-PFPN) is a novel positron emission tomography (PET) probe designed to specifically targets melanin. This study aimed to evaluate the diagnostic feasibility of F-PFPN in patients with ocular or orbital melanoma. Materials and Methods: Three patients with pathologically confirmed ocular or orbital melanoma (one male, two females; age 41–59 years) were retrospectively reviewed. Each patient underwent comprehensive F-PFPN and F-fluorodeoxyglucose (F-FDG) PET scans. The maximum standardized uptake value (SUV) of the lesion and the interference caused by background tissue were compared between F-PFPN and F-FDG PET imaging. In addition, the effect of intrinsic pigments in the uvea and retina on the interpretation of the results was examined. The contralateral non-tumorous eye of each patient served as a control. Results: All primary tumors (3/3) were detected using F-PFPN PET, while only two primary tumors were detected using F-FDG PET. Within each lesion, the SUV of F-PFPN was 2.6 to 8.3 times higher than that of F-FDG. Regarding the quality of PET imaging, the physiological uptake of F-FDG PET in the brain and periocular tissues limited the imaging of tumors. However, F-PFPN PET minimized this interference. Notably, intrinsic pigments in the uvea and retina did not cause abnormal concentrations of F-PFPN, as no anomalous uptake of F-PFPN was detected in the healthy contralateral eyes. Conclusion: Compared to F-FDG, F-PFPN demonstrated higher detection rates for ocular and orbital melanomas with minimal interference from surrounding tissues. This suggests that F-PFPN could be a promising clinical diagnostic tool for distinguishing malignant melanoma from benign pigmentation in ocular and orbital melanomas.