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Eluting Implants for Concurrent Chemotherapy and Radiotherapy: The Dosimetric Impact of Drug/Nanoparticles Elimination From Tumor

F Boateng1*, W Ngwa2 , (1) TIDTAC LLC, FL, (2) Harvard Medical School, Boston, MA


(Monday, 7/15/2019) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 1

Purpose: To investigate the dosimetric impact of drug/nanoparticles diffusion and elimination from tumor volume during concomitant chemoradiotherapy via drug/NP eluting implants/spacers for dose enhancement. To determine the feasibility of using drug/NP-eluting spacers for radiotherapy applications.

Methods: A proposed model was used to evaluate the dosimetric impact of drug/NP diffusion into the tumor and concurrent elimination from the tumor whiles eluting-spacer releases the preload for chemoradiotherapy application. A model for bioerodible eluting-spacer load with carboplatin nanoparticles (CaPN) of concentration 54 mg/g with elimination rate of 1.5E-4 1/min. An experimentally reported erosion rate constant (k = 5.5E-7 kgm^-2.s^-1) was used to study the release rates. An in vivo determined diffusion coefficient (2.2E-8 cm2/s) of nanoparticles (NP). The corresponding dose enhancement factors were evaluated.

Results: The results highlighted the superiority of drug eluting implant over systemic administration whiles accounting for drug/NP elimination from the tumor Volume. Also, NP/drug releasing profile for the spacer of large surface area (diameter 1.6 mm) was faster than spacer with smaller surface area (diameter of 0.8 mm) to 1.6 mm, which showed that the larger the surface area of eluting spacer the faster the drug/NP release rate. Dose enhancement factor (DEF) at tumor distance 5 mm for 50 kVp for CaPN diffusion into the tumor without elimination was higher (DEF = 6.14) compared to DEF = 4.17, for CaPN diffusion with elimination from the tumor. DEF for I-125 seed (DEF = 5.40) for CaPN without elimination compared to DEF = 3.71, for drug diffusion and elimination from the tumor.

Conclusion: The findings demonstrated that DEF depends on the amount of the drug/NP concentration present in the tumor. The longer the NP/drug remain in the tumor volume, the higher the DEF for a desired period. The results suggest that it is feasibility to use drug/NP-eluting spacers/implants for chemoradiotherapy applications.


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