Korean J Radiol.  2024 Aug;25(8):742-748. 10.3348/kjr.2024.0243.

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

• Wang Y
• Wang X
• Zhang J
• Zhang X
• Cheng Y
• Jiang F

• KMID: 2558280
• DOI: http://doi.org/10.3348/kjr.2024.0243

Abstract

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

Keyword

Ocular melanoma; Orbital melanoma; Positron emission tomography; ¹⁸F-FDG; ¹⁸F-PFPN