Gadolinium-doped iron oxide nanoparticles induced magnetic field hyperthermia combined with radiotherapy increases tumour response by vascular disruption and improved oxygenation

The gadolinium-doped iron oxide nanoparticles (GdIONP) with greater specific power adsorption rate (SAR) than Fe3O4 was developed and its potential application in tumour therapy and particle tracking were demonstrated in transgenic adenocarcinoma of the mouse prostate C1 (TRAMP-C1) tumours. The GdIONPs accumulated in tumour region during the treatment could be clearly tracked and quantified by T2-weighted MR imaging. The therapeutic effects of GdIONP-mediated hyperthermia alone or in combination with radiotherapy (RT) were also evaluated. A significant increase in the tumour growth time was observed following the treatment of thermotherapy (TT) only group (2.5 days), radiation therapy only group (4.5 days), and the combined radio-thermotherapy group (10 days). Immunohistochemical staining revealed a reduced hypoxia region with vascular disruption and extensive tumour necrosis following the combined radio-thermotherapy. These results indicate that GdIONP-mediated hyperthermia can improve the efficacy of RT by its dual functions in high temperature (temperature greater than 45 degrees C)-mediated thermal ablation and mild-temperature hyperthermia (MTH) (temperature between 39 and 42 degrees C)-mediated reoxygenation.