A Novel Melanin-Targeted 18 F-PFPN Positron Emission Tomography Imaging for Diagnosing Ocular and Orbital Melanoma.

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.
Competing Interests: The authors have no potential conflicts of interest to disclose.
(Copyright © 2024 The Korean Society of Radiology.)