期刊
CANCERS
卷 13, 期 12, 页码 -出版社
MDPI
DOI: 10.3390/cancers13122997
关键词
double strand break; enzymatic double strand break; cell survival; hypoxia; relative biological effectiveness
类别
资金
- Chung Shan Medical University, Taichung, Taiwan [CSMU-INT-109-08]
- Linkou-Chang Gung Memorial Hospital [CMRPD1H0473, CMRPD1J0322]
- Ministry of Sciences and Technology, Taiwan [MOST 109-2314-B-182-078-MY3, 109-2628-B-182-008]
The study proposes an algorithm to estimate the relative biological effectiveness (RBE) of proton beams for cell survival under different oxygen conditions, with RBE values varying with linear energy transfer (LET) ranges. The RBE values under severe hypoxia are higher, indicating a greater contribution of direct effects from protons.
Simple Summary This study presents an algorithm to estimate the relative biological effectiveness (RBE) for cell survival under hypoxic conditions using the repair-misrepair-fixation model. The study finds that the RBE values are in the range of 1.0-3.0 for the linear energy transfer equal to 1.1 to 22.6 keV/mu m under aerobic condition (21% O-2) and further increase to the range of 1.1-4.4 under severe hypoxia (0.1% O-2). This study uses the yields of double-strand breaks (DSBs) to determine the relative biological effectiveness (RBE) of proton beams, using cell survival as a biological endpoint. DSB induction is determined when cells locate at different depths (6 positions) along the track of 62 MeV proton beams. The DNA damage yields are estimated using Monte Carlo Damage Simulation (MCDS) software. The repair outcomes are estimated using Monte Carlo excision repair (MCER) simulations. The RBE for cell survival at different oxygen concentrations is calculated using the repair-misrepair-fixation (RMF) model. Using Co-60 gamma-rays (linear energy transfer (LET) = 2.4 keV/mu m) as the reference radiation, the RBE for DSB induction and enzymatic DSB under aerobic condition (21% O-2) are in the range 1.0-1.5 and 1.0-1.6 along the track depth, respectively. In accord with RBE obtained from experimental data, RMF model-derived RBE values for cell survival are in the range of 1.0-3.0. The oxygen enhancement ratio (OER) for cell survival (10%) decreases from 3.0 to 2.5 as LET increases from 1.1 to 22.6 keV/mu m. The RBE values for severe hypoxia (0.1% O-2) are in the range of 1.1-4.4 as LET increases, indicating greater contributions of direct effects for protons. Compared with photon therapy, the overall effect of 62 MeV proton beams results in greater cell death and is further intensified under hypoxic conditions.
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