Targeting liver tumors with hyperthermia: Ferromagnetic embolization in a rabbit liver tumor model

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Abstract
Background and Objectives: Ferromagnetic embolization hyperthermia (FEH) consists of arterially embolizing liver tumors with ferromagnetic particles, and then applying an external alternating magnetic field to generate hysteretic heating within the embolized particles. The objective of this study was to assess the ability of FEH to selectively target liver tumors with hyperthermia. Methods: Twenty rabbits containing hepatic VX2 carcinomas were arterially infused with ferromagnetic particles suspended in lipiodol, and then exposed to an external alternating magnetic field. Temperatures in the tumor, normal hepatic parenchyma (NHP), and rectum were recorded. Tumour and NHP were chemically analyzed for iron content, which was then correlated with the observed heating rates. Results: The mean tumor‐to‐NHP iron concentration ratio was 5.3:1 (P < 0.001, N = 20). The mean tumor heating rates were 3.0–11.5 times greater than those in the NHP (P < 0.001, N = 20). After 5 min of heating, the greatest increase in mean tumor temperature was 11.0°C and the greatest increase in mean NHP temperature was 1.3°C. There was a positive relationship between tumor iron concentration and heating rate (correlation coefficient = 0.82, P < 0.001, N = 20). A tumor iron concentration of 2–3 mg/g resulted in tumor heating rates of 0.5–1.0°C/min. Conclusions: Hepatic arterial infusion of lipiodol containing ferromagnetic particles can result in excellent targeting of liver tumors with hyperthermia on the subsequent application of an external alternating magnetic field. The promising results of this study warrant further investigation of FEH as a potential treatment for advanced liver cancer. J. Surg. Oncol. 2001;78:22–29.