Promising magnetic nanoradiosensitizers for combination of tumor hyperthermia and x-ray therapy: Theoretical calculation

Nanoparticle (NP) assisted magnetic hyperthermia (NMH) is a clinically proven method for cancer treatment. High-Z magnetic NPs could also be a perspective object for combining hyperthermia with tumor radiosensitization. However, this application of NPs is little studied, and it is unclear as to what particle compositions one can rely on. Therefore, the present work focuses on the search of materials that combine alternating magnetic field induced heating and high atomic number related dose enhancement abilities. A theoretical evaluation of 24 promising NP compositions was performed: the values of dose enhancement factor (DEF) were determined for kilovoltage x-ray spectra (30–300 kVp), as well as specific absorption rate (SAR) values were calculated for various combinations of elemental compositions and particle size distributions. For the alternating magnetic fields with amplitude 75–200Oe and frequency 100kHz, the maximum obtained SAR values ranged from 0.35 to 6000Wg−1, while DEF values for studied compounds ranged from 1.07 to 1.59. The increase in the monodispersity of NPs led to a higher SAR, confirming well-known experimental data. The four types of SAR dependences on external magnetic field amplitude and anisotropy constant were found for various particle sizes. The most predictable SAR behavior corresponds to larger NPs (∼70–100 nm). Thus, based on these calculations, the most promising for the combination of NMH with radiotherapy, from a physical point of view, are La0.75Sr0.25MnO3, Gd5Si4, SmCo5, and Fe50Rh50. The greatest dose enhancement is expected for superficial radiotherapy (in the voltage range up to ∼60 kVp).