4-Borono-2-[18F]fluoro-d,l-phenylalanine: a possible tracer for melanoma diagnosis with PET

The potential of 4-borono-2-¹⁸F]fluoro-d,l-phenylalanine (¹⁸F]FBPA), a fluorinated derivative of a target compound for boron neutron capture therapy, for melanoma imaging by positron emission tomography (PET) was studied using animal models. A high uptake of ¹⁸F]FBPA was found in murine B16 melanoma or in Greene's melanoma No. 179, a melanotic cell line in hamsters, for the first 6 h after injection. Whole body autoradiography using ¹⁸F]FBPA gave a clear image of the B16 tumor. The acid-insoluble ¹⁸F in the B16 increased to 27% by 6h, and most of the free ¹⁸F was detected as ¹⁸F]FBPA in both B16 and plasma. In the hamster models, No. 179 showed a 1.7 times higher uptake than amelanotic Greene's melanoma No. 178 at 6 h post-injection, although both melanomas indicated similar metabolic activities when examined by a tracer uptake study using l-¹⁴C]methionine, 2-deoxy-d-¹⁴C]glucose and ³H]thymidine. ¹⁸F]FBPA may be a very promising PET tracer for melanoma imaging.