Nanoparticle-aided
radiation therapy is emerging as a promising modality to enhance
radiotherapy via the radiosensitizing action of high atomic number (Z) nanoparticles. However, the delivery of sufficiently potent concentrations of such nanoparticles to the
tumor remain a challenge. This study investigates the dose enhancement to lung
tumors due to high-Z nanoparticles (NPs) administered via inhalation during external beam
radiotherapy. Here NPs investigated include:
cisplatin nanoparticles (CNPs),
carboplatin nanoparticles (CBNPs), and
gold nanoparticles (GNPs). Using Monte Carlo-generated megavoltage energy spectra, a previously employed analytic method was used to estimate dose enhancement to lung
tumors due to radiation-induced photoelectrons from the NPs administered via inhalation route (IR) in comparison to intravenous (IV) administration. Previous studies have indicated about 5% of FDA-approved
cisplatin concentrations reach the lung via IV. Meanwhile recent experimental studies indicate that 3.5-14.6 times higher concentrations of NPs can reach the lung by IR compared to IV. Taking these into account, the dose enhancement factor (
DEF) defined as the ratio of the
radiotherapy dose with and without nanoparticles was calculated for a range of NPs concentrations and
tumor sizes. The
DEF for IR was then compared with that for IV. For IR with 3.5 times higher concentrations than IV, and 2 cm diameter
tumor, clinically significant
DEF values of up to 1.19, 1.26, and 1.51 were obtained for CNPs, CBNPs and GNPs. In comparison values of 1.06, 1.08, and 1.15 were obtained via IV administration. For IR with 14.6 times higher concentrations, even higher
DEF values were obtained e.g. 1.81 for CNPs. Results also showed that the
DEF increased with increasing field size or decreasing
tumor volume, as expected. The results of this work indicate that IR administration of targeted high-Z CNPs/CBNPs/GNPs could enable clinically significant
DEF to lung
tumors compared to IV administration during external beam
radiotherapy. For FDA approved concentrations of CNPs or CBNPs considered, this could allow for additional dose enhancement to
tumors via photoelectric mechanism during
concomitant chemoradiotherapy.