Brachytherapy Application With In Situ Dose Painting Administered by Gold Nanoparticle Eluters

Abstract

Purpose Recent studies show promise that administering gold nanoparticles (GNP) to tumor cells during brachytherapy could significantly enhance radiation damage to the tumor. A proposed new strategy for sustained administration of the GNP in prostate tumors is to load them into routinely used brachytherapy spacers for customizable in-situ release after implantation. This in silico study investigates the intra-tumor biodistribution and corresponding dose enhancement over time due to GNP released from such GNP-loaded brachytherapy spacers (GBS). Method and Materials An experimentally determined intra-tumoral diffusion coefficient (D) for 10 nm nanoparticles was employed to estimate D for other sizes using the Stoke-Einstein equation. GNP concentration profiles, obtained using D, were then employed to calculate the corresponding dose enhancement factor (DEF) for each tumor voxel using dose-painting by numbers approach, for times relevant to the considered brachytherapy sources' lifetimes. The investigation is carried out as a function of GNP size for clinically applicable low dose rate brachytherapy sources: I-125, Pd-103, Cs-131. Results Results showed that dose enhancement to tumor voxels/sub-volumes during brachytherapy can be customized by varying the sizes of GNP released or eluted from the GBS. For example, using 7 mg/g GNP concentration, significant DEF (> 20%) could be achieved 5 mm from a GBS after 5, 12, 25, 46, 72, 120, and 195 days, respectively, for GNPs sizes of 2 nm, 5 nm, 10 nm, 20 nm, 30 nm 50 nm, and 80 nm when treating with I-125. Conclusions Analyses show that using Cs-131 provides the highest dose enhancement to tumor voxels. However, given its relatively longer half-life, I-125 presents the most flexibility for customizing the dose enhancement as a function of GNP size. The findings provide a useful reference for further work towards potential development of a new brachytherapy application with in-situ dose-painting administered via gold-nanoparticle eluters, for prostate cancer.

Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI)

“…Fick’s law of diffusion is used to determine the initial concentration of CONPs needed to achieve a minimum concentration for radioprotection at different distances from the lumpectomy cavity during APBI. The concentration of NPs as a function of distance, x , and time, t , for different sizes of NP is given by the solution of Fick’s second law of diffusion [20]: $$C(x,t)=C_{s}true[1-erftrue(\frac{x}{2\sqrt{Dt}}true)true]$$ where C s is the initial concentration at the wall of the lumpectomy cavity and is defined as the concentration of the CONPs present in the balloon coating; both the polymer and breast tissue are considered as water-equivalent. Here, the concentration of NPs originally present in breast tissue is assumed to be zero.…”

Using immunotherapy to boost the abscopal effect

“…These Auger electrons have high LET and the potential to inflict more irreparable mutations upon tumour cell DNA, which could help by increasing tumour immunogenicity or overcoming immunosuppressive hypoxia 2,80,81 .…”

Functional Radiotherapy Targeting using Focused Dose Escalation

“…Both low dose rate permanent source placement and high dose rate temporary after-loading techniques can be used to achieve focused boosting using brachytherapy [61,75]. In many departments, a pragmatic decision is made as to which method to use, based upon availability and experience with a particular technique.…”