Feasibility study of high-temperature thermoseed inductive hyperthermia in melanoma treatment

Current treatment modalities for melanoma do not offer satisfactory efficacy. We have developed a new, minimally invasive hyperthermia technology based on radio-frequency hyperthermia. Herein, we investigated the feasibility of using a nickel-copper thermoseed for inductive hyperthermia at a relatively high temperature (46-55 ˚C). In vitro, the thermoseed showed good thermal effects and effective killing of B16/F10 melanoma cells. Temperatures of 53.1 ± 0.5 ˚C were achieved for a single thermoseed and 56.5 ± 0.5 ˚C for two in parallel (spacing 5 mm). No B16/F10 melanoma cells survived with heating time longer than 20 min in the parallel thermoseed group. Magnetic fields or thermoseeds alone did not affect the survival rate of B16/F10 cells (P>0.05). In vivo, B16/F10 melanoma cells were subcutaneously injected into the right axilla of C57BL/6 mice. After the tumors grew to ~11-13 mm, two thermoseeds (spacing 5 mm) were implanted into the tumors and the mice were subjected to an alternating magnetic field (100-250 kHz, 15 kA/m) to induce hyperthermia. The temperature at the center of the tumor reached 46 ˚C at 5 min and plateaued at 50 ˚C. Thermoseed treatment produced large necrotic areas, inhibited tumor growth in 60% (6 of 10) of animals and prolonged survival time (P<0.05). Thus, with further optimization and testing, high-temperature thermoseed inductive hyperthermia may have therapeutic potential for melanoma.