Melanin-targeted [18F]-PFPN PET imaging may shed light for clear cell sarcoma

Purpose Intracytoplasmic melanin pigment is a characteristic of clear cell sarcoma (CCS), which is a particularly deadly type of soft-tissue sarcoma. [F-18]-N-(2-(diethylamino)ethyl)-5-(2-(2-(2-fluoroethoxy)ethoxy)ethoxy)picolinamide ([F-18]-PFPN) is a positron emission tomography (PET) probe characterized by high melanin affinity. Therefore, this study aimed to investigate the feasibility of melanin-targeted [F-18]-PFPN PET in patients with CCS.Methods This prospective single-centre study recruited patients with pathologically confirmed CCS. [F-18]-FDG PET/computed tomography and [F-18]-PFPN PET/magnetic resonance imaging scans were performed within 1 week of each other. The lesion numbers and [F-18]-FDG and [F-18]-PFPN PET parameters (maximum standardized uptake value [SUVmax], mean standardized uptake value [SUVmean], metabolic/melanotic tumour volume [MTV/MLTV], and total lesion glycolysis/melanin [TLG/TLM]) were collected.Results Three patients with CCS were recruited and received PET imaging. A total of 56 lesions were detected on [F-18]-PFPN PET, including primary tumour and distant metastases. Identical lesions were not detected on [F-18]-PFPN and [F-18]-FDG PET. Twelve lesions (12/39, 30.77%) on [F-18]-FDG imaging were missed on [F-18]-PFPN, and 20 lesions (20/47, 42.55%) on [F-18]-PFPN imaging were missed on [F-18]-FDG. In quantitative analysis, the [F-18]-FDG SUVmean (4.60 +/- 3.24) was higher than the [F-18]-PFPN SUVmean (3.0 +/- 2.63) in all lesions (P=0.01). No significant correlations were found between the SUVmax, SUVmean, MLTV/MTV, and TLM/TLG values of [F-18]-PFPN and [F-18]-FDG (P>0.05).Conclusion Melanin-targeted [F-18]-PFPN PET imaging is feasible for the diagnosis of CCS. Different imaging features were displayed on [F-18]-PFPN and [F-18]-FDG PET imaging, demonstrating the complementary role of the tracers. Combined use of the two imaging modalities would be preferred in patients with CCS.

Automated summary

This study investigates the feasibility of melanin-targeted [F-18]-PFPN PET in patients with clear cell sarcoma (CCS). The results demonstrate that this technique is effective in diagnosing CCS and complements other PET modalities.