Abstract
BackgroundRelative biological effectiveness (RBE) is a key quantity for the description of radiobiological effects induced by charged-particle irradiation in the context of ion-beam cancer therapy. Since RBE is a complex function that depends on different physical, chemical, and biological parameters, a fundamental understanding of radiobiological effects becomes increasingly important for clinical applications. The phenomenon-based multiscale approach to the physics of radiation damage with ions (MSA) provides a tool for a molecular-level understanding of physical and chemical mechanisms of radiation biodamage and allows for quantification of macroscopic biological effects caused by ion irradiation. This study reports the first application of the MSA for the analysis of RBE of ion beams.ResultsAs a case study, we quantify the response of human and rodent normal cells to carbon-ion irradiation at different values of linear energy transfer (LET). Clonogenic cell survival as a function of dose, RBE at a 10% survival level as well as other radiobiological parameters, such as the cross section of cell inactivation, are analyzed and compared with experimental data. The MSA is used also to evaluate RBE at high values of LET where RBE decreases due to the “overkill” effect. In this regime, the dose needed to achieve a given biological effect is deposited by only a few ions and the RBE becomes inversely proportional to LET.ConclusionsGood agreement with a large set of experimental data on clonogenic cell survival, inactivation cross section, and RBE emphasizes the predictive power of the MSA. In the high-LET regime, the fact that a given number of ions may produce more damage than needed for a given biological effect leads to a significant (up to 20%) variation in RBE. Consideration of this effect in the analysis of experimental data on irradiation with high-LET ions may lead to re-evaluation of RBE in this regime.
Highlights
Relative biological effectiveness (RBE) is a key quantity for the description of radiobiological effects induced by charged-particle irradiation in the context of ion-beam cancer therapy
Good agreement with a large set of experimental data on clonogenic cell survival, inactivation cross section, and RBE emphasizes the predictive power of the MSA
In the high-linear energy transfer (LET) regime, the fact that a given number of ions may produce more damage than needed for a given biological effect leads to a significant variation in RBE
Summary
We quantify the response of human and rodent normal cells to carbon-ion irradiation at different values of linear energy transfer (LET). Clonogenic cell survival as a function of dose, RBE at a 10% survival level as well as other radiobiological parameters, such as the cross section of cell inactivation, are analyzed and compared with experimental data. The MSA is used to evaluate RBE at high values of LET where RBE decreases due to the “overkill” effect. In this regime, the dose needed to achieve a given biological effect is deposited by only a few ions and the RBE becomes inversely proportional to LET
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