Speaker
Description
To improve the efficacy of radiotherapy one of the objective is to increase the dose delivered to the tumour while sparing the surrounding healthy tissues. The strategy we have used consists in loading the tumorwith high-Z elements such as metallic nanoparticles in combination with low energy radiations. Indeed, for low energy radiations (keVrange) the absorption coefficient of heavy elements is higher than that of normal tissues (assimilated as water) and thus the deposited energy is increased proportionally to the heavy element concentration. The photoelectric effect thus induced generates photo and Auger electrons that locally, around the heavy element significantly increase the dose delivered. Such an effect could be compared to the one produced by high Linear Energy Transfer particles, increasing locally the production of radicals.
We thus have evaluated the efficacy of several heavy atoms containing molecules or nanoparticles and efforts have been made to better understand the undergoing mechanisms responsible for the observed radiosensitization effect [1-3]. Using dosimetric gels or oxidative DNA lesions as biomarkers, we have shown that in vitro, the deposited dose increases linearly with the heavy atom concentration and experimental data were found to be in agreement with theoretical ones. More recently, experiments were conducted with nanoscintillators having the properties to emit UV light upon exposure to X-irradiation. These nanoscintillators containing heavy atoms, also induce a significant radiation dose enhancement at least in vitro[4]. However while UV-photon emission could be observed experimentally when the powder of the nanoscintillators was irradiated, we could not detect any specific UV-induced DNA lesions when aqueous DNA solutions are irradiated in presence of the nanoscintillators. Such results strongly suggest that the amount of produced UV-photon is too low to generate significant levels of DNA lesions.
REFERENCES
[1] L. Bobyk, M. Edouard, P. Deman, J. Rousseau, J.F. Adam, J.L. Ravanat, F. Esteve, J. Balosso, R.F. Barth, H. Elleaume, J. Exp. Clin. Cancer Res., 31 (2012) 78.
[2] R. Delorme, F. Taupin, M. Flaender, J.L. Ravanat, C. Champion, M. Agelou, H. Elleaume, Med Phys, 44 (2017) 5949-5960.
[3] F. Taupin, M. Flaender, R. Delorme, T. Brochard, J.F. Mayol, J. Arnaud, P. Perriat, L. Sancey, F. Lux, R.F. Barth, M. Carriere, J.L. Ravanat, H. Elleaume, Phys. Med. Biol., 60 (2015) 4449-4464.
[4] A.-L. Bulin, M. Broekgaarden, F. Chaput, V. Baisamy, J. Garrevoet, B. Busser, D. Brueckner, A. Youssef, J.-L. Ravanat, C. Dujardin, V. Motto-Ros, F. Lerouge, S. Bohic, L. Sancey, H. Elleaume, Advanced Science, 7 (2020) 2001675.