The effects of cell displacement on DNA damages in targeted radiation therapy using Geant4-DNA

Charged particle radiation can, directly and indirectly, affect cells by breaking DNA strands. This effect includes DNA single-strand breaks (SSB) and DNA double-strand breaks (DSB), which may cause cell death and mitotic failure. Thus, using short-range charged particles such as Auger electrons (AEs) not only leads to the destruction of the target cell but also prevents the nearby healthy cells from exposing to ionizing radiation. In this study, two spherical cells (C and C₂) and their cell nucleus, both made of liquid water, were modeled. An atomic DNA model constructed in the Geant4-DNA Monte Carlo (MC) simulation toolkit was placed inside the nucleus of the C and C₂ cells. The number of direct and indirect SSB, DSB, and hybrid DSB (HDSB), caused by some of the most widely-used Auger electron-emitting (AEE) radionuclides, including ^99mTc, ¹¹¹In, ¹²³I, ¹²⁵I, and ²⁰¹Tl, distributed within different compartments of the C cell, was calculated in the C and C₂ cells, considering the distance between the surface of the two cells ranges from 0 to 5 μm. The present work aimed to investigate the biological effects of AEE radionuclides and their potential for cancer treatment through targeted radiation therapy. The results indicate the impact of ²⁰¹Tl > ¹²⁵I > ¹²³I > ¹¹¹In > ^99mTc on DNA damage when the target is C (first spherical cell). On the other hand, for C₂ at distances of 0 to 5 μm, the impact of ^99mTc > ¹²³I > ¹¹¹In > ²⁰¹Tl > ¹²⁵I on DNA damage is observed.