Radiotherapy is a proven skin cancer treatment modality with cure rates comparable to surgery. To make sure of its effectiveness while being safe, it is necessary to provide conformal dose coverage at the target (tumour) while sparing the surrounding normal tissues. Target dose escalation is therefore needed to increase the tumour control probability, but at the same time decrease normal tissue complication probabilities for organs-at-risk (OARs). Under such circumstances, nanoparticle-enhanced radiotherapy is suggested for providing dose enhancement in the target.
Xiao J Zheng and James C L Chow in their study “Radiation dose enhancement in skin therapy with nanoparticle addition: A Monte Carlo study on kilovoltage photon and megavoltage electron beams” investigated the dose enhancement due to the incorporation of nanoparticles in skin therapy using the kilovoltage (kV) photon and megavoltage (MV) electron beams produced by an Xstrahl 200 orthovoltage unit and a Varian 21 EX linear accelerator respectively. Monte Carlo simulations were used to predict the dose enhancement when different types and concentrations of nanoparticles were added to skin target layers of varying thickness.
It was found that among all nanoparticles, Au had the highest DER (5.2-6.3) when irradiated with kV photon beams. Dependence of the DER on the target layer thickness was not significant for the 220 kVp photon beam but it was for 105 kVp beam for Au nanoparticle concentrations higher than 18 mg/mL. For other nanoparticles, the DER was dependent on the atomic number of the nanoparticle and energy spectrum of the photon beams. All nanoparticles showed an increase of DER with nanoparticle concentration during the photon beam irradiations regardless of thickness. For electron beams, the Au nanoparticles were found to have the highest DER (1.01-1.08) when the beam energy was equal to 4 MeV, but this was drastically lower than the DER values found using photon beams. The DER was also found affected by the depth of maximum dose of the electron beam and target thickness. For other nanoparticles with lower atomic number, DERs in the range of 0.99-1.02 were found using the 4 and 6 MeV electron beams.
The authors concluded that in nanoparticle-enhanced skin therapy, Au nanoparticle addition can achieve the highest dose enhancement with 105 kVp photon beams. Electron beams, while popular for skin therapy, did not produce as high dose enhancements.
This Xstrahl In Action was adapted from a article found on a National Library of Medicine website.