Abstract
OBJECTIVE: (18)F-N-(2-(Diethylamino)ethyl)-5-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy) picolinamide ((18)F-PFPN) is a novel positron emission tomography (PET) probe designed to specifically targets melanin. This study aimed to evaluate the diagnostic feasibility of (18)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 (18)F-PFPN and (18)F-fluorodeoxyglucose ((18)F-FDG) PET scans. The maximum standardized uptake value (SUV(max)) of the lesion and the interference caused by background tissue were compared between (18)F-PFPN and (18)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 (18)F-PFPN PET, while only two primary tumors were detected using (18)F-FDG PET. Within each lesion, the SUV(max) of (18)F-PFPN was 2.6 to 8.3 times higher than that of (18)F-FDG. Regarding the quality of PET imaging, the physiological uptake of (18)F-FDG PET in the brain and periocular tissues limited the imaging of tumors. However, (18)F-PFPN PET minimized this interference. Notably, intrinsic pigments in the uvea and retina did not cause abnormal concentrations of (18)F-PFPN, as no anomalous uptake of (18)F-PFPN was detected in the healthy contralateral eyes. CONCLUSION: Compared to (18)F-FDG, (18)F-PFPN demonstrated higher detection rates for ocular and orbital melanomas with minimal interference from surrounding tissues. This suggests that (18)F-PFPN could be a promising clinical diagnostic tool for distinguishing malignant melanoma from benign pigmentation in ocular and orbital melanomas.