Effect of local hyperthermia induced by nanometer magnetic fluid on the rabbit VX2 liver tumor model

Hyperthermia induced by magnetic nanoparticles is a recent therapeutic approach for local targeting of hyperthermia and thermoablation and is a promising treatment of malignant tumors. The purpose of this study is to evaluate the potential and therapeutic effect of magnetic fluid hyperthermia on the rabbit VX2 liver tumor model. Rabbits bearing liver tumors 14 days after tumor implantation were randomly divided into five groups of 10 cases each, including three control groups and two hyperthermia groups. Hyperthermia was carried out immediately after a single intratumoral injection of uncoated water-based Fe3O4 magnetic fluid under an alternating magnetic field only once as one hyperthermia group and repeated hyperthermia after 5 days as the other treated group. The distribution of magnetic fluid was evaluated by CT scanning. All animals were sacrificed 4 weeks after tumor implantation. The therapeutic effect was determined by tumor size and macroscopic and pathological examination of the liver tumor. The local higher density imaging of intratumoral magnetic fluid deposits compared to the surrounding tissue was clearly observed by CT scanning. Twenty-eight days after tumor implantation, the tumor maximal diameter and tumor volume of two hyperthermia were both significantly less than those of control groups (P < 0.05). Tumor volume inhibition by single or repeated hyperthermia compared to the three control groups was 71.93–79.91% and 92.34–94.46% (P < 0.05), respectively. Under a microscope, coagulation necrosis was observed in the heated area, which had a clear boundary line with the surrounding tissue. The intratumoral distribution of magnetic nanoparticles, especially in the area of necrosis, appeared much more homogenous than in the untreated ones. This study demonstrates that hyperthermia induced by direct intratumoral injection of magnetic fluid can be used safely, and a well-homogenized distribution of high intratumoral temperature without heating adjacent to normal tissue can be achieved.