Improved detection of regional melanoma metastasis using 18F-6-Fluoro-N-[2-(Diethylamino)Ethyl] Pyridine-3-Carboxamide, a Melanin-specific PET probe,  by perilesional administration

The efficacy of differing routes of administration of 18F-6-fluoro-N-[2-(diethylamino)ethyl] pyridine-3-carboxamide (18F-MEL050), a new benzamide-based PET radiotracer for imaging regional lymph node metastasis in melanoma, was assessed. Methods: B16-Black/6 metastatic melanoma cells harboring an mCherry transgene were implanted into the left-upper-foot surface of 49 C57 Black/6 mice as a model of popliteal lymph node (PLN) metastasis. Ultrasound scanning of the left PLN was performed at baseline and in combination with 18F-MEL050 PET on days 5, 9, and 14. Mice were divided into 2 groups to compare the results of tracer administration either subcutaneously at the tumor site (local) or in the lateral tail vein (systemic). After PET on each imaging day, 5 mice per group—including any with evidence of metastasis—were sacrificed for ex vivo validation studies including assessment of retained radioactivity and presence of the mCherry transgene as a surrogate of nodal tumor burden. Results: Nine mice were judged as positive for PLN metastasis by ultrasound at day 5, and 8 PLNs were positive on 18F-MEL050 PET, 3 after systemic and 5 after local administration. Ex vivo analysis showed that ultrasound correctly identified 90% of positive PLNs, with 1 false-positive. 18F-MEL050 PET correctly identified 60% of positive PLNs after systemic administration and 100% after local administration with no false-positive results by either route. The average node-to-background ratio for positive PLNs was 6.8 in the systemic-administration group and correlated with disease burden. In the local-administration group, the mean uptake ratio was 48, without clear relation to metastatic burden. Additional sites of metastatic disease were also correctly identified by 18F-MEL050 PET. Conclusion: In addition to its potential for systemic staging, perilesional administration of 18F-MEL050 may allow sensitive and specific, noninvasive identification of regional lymph node metastasis in pigmented malignant melanomas. © 2011, Society of Nuclear Medicine

Keywords

Neoplasms, Mice, Positron computed tomography, Tracer techniques, Melanin, Radioactivity

Citation

Denoyer, D., Potdevin, T., Roselt, P., Neels, O. C., Kirby, L., Greguric, I., Katsifis, A., Dorow, D. S., & Hicks, R. J. (2011). Improved detection of regional melanoma metastasis using 18F-6-Fluoro-N-[2-(Diethylamino)Ethyl] Pyridine-3-carboxamide, a melanin-specific PET probe, by perilesional administration. Journal of Nuclear Medicine, 52(1), 115-122. doi:10.2967/jnumed.110.078154