| dc.description.abstract | Micro-metastases are a significant problem in cancer therapy. These are cell clusters that can be found throughout the body, often arising from the primary tumor. They can go on to form radiologically discernable metastases. Our understanding of metastatic cancer is evolving, and therapeutic strategies need to evolve with it.
Gold nanoparticles have been extensively used in the medical field. In this study, gold nanoparticles containing Auger emitting radionuclides of 125I or 117mSn were modeled for the treatment of micro-metastatic cancer. The Monte Carlo transport code Geant4-DNA was used to model the decay of these radioactive atoms, following each of the emissions along its particle track down to thermal energies. This open source “track structure” code was able to keep a detailed spatiotemporal report of energy depositions and secondary particle formation. The energy deposition data generated was visualized using the software VisIt.
It was found that both radionuclides contained adequate energy for the treatment of circulating tumor cells and micro-metastases. However, depending upon micro-metastatic tumor volume, they have different benefits. The energy deposition from 125I is much denser overall when there are a large number of decays. Compared to that, 117mSn has a less dense energy deposition for a large number of decays, but individual decays were generally a higher energy.
The present analysis showed that very low energy electrons will not escape from the gold nanoparticle itself; they would excite tertiary particles and create thermal energy themselves, on the order of a few eV. The cascade of electrons generates what is commonly referred to as a Coulomb explosion, inducing significant direct damage to molecules adjacent to the gold nanoparticle. The electrons that escape the gold nanoparticle would go on to also induce direct damage to the DNA if the particle is within several angstroms, or create free radicals if it is not. Based on the number of free radicals generated, indirect damage to the DNA of the cancerous lesion would also be quite substantial. The resulting dose enhancement indicates that use of radioactive gold nanoparticles for the therapeutic treatment of micro-metastatic cancer can be an excellent treatment strategy. | en |
