Application of a simple DNA damage model developed for electrons to proton irradiation

Matsuya, Yusuke  ; Kai, Takeshi   ; Parisi, A.*; Yoshii, Yuji*; Sato, Tatsuhiko   

Proton beam therapy allows to irradiate tumor volumes with reduced side effects on normal tissues with respect to X-ray radiotherapy. Biological effects such as cell killing after proton beam irradiations depend on the proton kinetic energy, which is intrinsically related in the early DNA damage induction. As such, the estimation of DNA damage yields based on Monte Carlo simulations is a research topic of worldwide interest. In this study, we investigate the possibility of applying a simple model developed for electron to proton without any modification. The yields of single-strand breaks (SSB), double-strand breaks (DSB) and the complex DSB were assessed as a function of the proton kinetic energy. The PHITS-based estimation accurately reproduced the experimental and simulated yields of various DNA damage types induced by protons with linear energy transfer (LET) up to about 30 keV/m. These results suggest that current DNA damage model implemented in PHITS is sufficient for estimating DNA lesion yields induced after protons irradiation except for lower energies than MeV.