Feasibility Study on the Radiation Dose by Radioactive Magnetic Core-Shell Nanoparticles for Open-Source Brachytherapy

SIMPLE SUMMARY: Breast cancer is the most prevalent cancer in women across the world. Most of these patients are diagnosed in an early stage, having only one small tumor. Treatment for these early-stage tumors often includes surgery followed by external beam radiotherapy. While highly effective, this treatment can be time-consuming, taking a few months to complete. This work investigates a new treatment where surgery is replaced by thermal ablation using magnetic nanoparticles. By making these nanoparticles also radioactive, radiotherapy and thermal ablation can be combined in one single treatment. We have investigated the radiation dose profiles of these radioactive magnetic nanoparticles using Monte Carlo computer simulations. It was found that the dose profiles are similar to commercial radioactive sources already used in the clinic. This indicates that the nanoparticles are suited to deliver a clinical dose to the patient, bringing this new treatment a step closer to introduction into the clinic. ABSTRACT: Background: Treatment of early-stage breast cancer currently includes surgical removal of the tumor and (partial) breast irradiation of the tumor site performed at fractionated dose. Although highly effective, this treatment is exhaustive for both patient and clinic. In this study, the theoretical potential of an alternative treatment combining thermal ablation with low dose rate (LDR) brachytherapy using radioactive magnetic nanoparticles (RMNPs) containing 103-palladium was researched. Methods: The radiation dose characteristics and emission spectra of a single RMNP were calculated, and dose distributions of a commercial brachytherapy seed and an RMNP brachytherapy seed were simulated using Geant4 Monte Carlo toolkit. Results: It was found that the RMNP seeds deliver a therapeutic dose similar to currently used commercial seed, while the dose distribution shows a spherical fall off compared to the more inhomogeneous dose distribution of the commercial seed. Changes in shell thickness only changed the dose profile between 2 × 10(−4) mm and 3 × 10(−4) mm radial distance to the RMNP, not effecting long-range dose. Conclusion: The dose distribution of the RMNP seed is comparable with current commercial brachytherapy seeds, while anisotropy of the dose distribution is reduced. Because this reduces the dependency of the dose distribution on the orientation of the seed, their surgical placement is easier. This supports the feasibility of the clinical application of the proposed novel treatment modality.