Antitumor effect of new local hyperthermia using dextran magnetite complex in hamster tongue carcinoma

OBJECTIVE: This study was performed to clarify the usefulness of Dextran magnetite (DM) for the oral cancer hyperthermia. METHODS: Tumors were induced in golden hamster tongue by 9,10-dimethyl 1-1,2-benzanthracene (DMBA) application. DM suspension was locally injected into the tumor-bearing tongue and tongues were heated up to 43.0-45.0degreesC, by AC magnetic field of 500 kHz. RESULTS: The average time taken for the temperature to rise to 43.0degreesC or above was 162 s (n = 17) at the margin of the tumor and 420 s (n = 17) at the center of the tumor. According to the tumor volume, the time required for an increase in the central temperature of tumor to 43.0degreesC tended to be prolonged. Both temperatures could be maintained at approximately 43.0-45.0degreesC for 30 min. The inhibition of the growth of tongue carcinoma in the four-time heating group was significantly greater than in the control group (P < 0.01). Moreover, the survival rate was significantly higher in the heated groups than in the control group (P < 0.01). Histological examination revealed a brown uniform DM accumulation at the stroma in the margin of the tumors. Many of tumor cells disappeared at the site adjacent to this accumulation. CONCLUSION: These results strongly suggest the usefulness of this local hyperthermic system in the oral region that is accessible to this treatment.