Department of Physics and Technology, University of Bergen, Bergen, Norway. Author to whom any correspondence should be addressed.
Phys Med Biol. 2018 Sep 13;63(18):185013. doi: 10.1088/1361-6560/aad9db.
The relative biological effectiveness (RBE) of protons varies with multiple physical and biological factors. Phenomenological RBE models have been developed to include such factors in the estimation of a variable RBE, in contrast to the clinically applied constant RBE of 1.1. In this study, eleven published phenomenological RBE models and two plan-based models were explored and applied to simulated patient cases. All models were analysed with respect to the distribution and range of linear energy transfer (LET) and reference radiation fractionation sensitivity ((α/β) ) of their respective experimental databases. Proton therapy plans for a spread-out Bragg peak in water and three patient cases (prostate adenocarcinoma, pituitary adenoma and thoracic sarcoma) were optimised using an RBE of 1.1 in the Eclipse treatment planning system prior to recalculation and modelling in the FLUKA Monte Carlo code. Model estimated dose-volume parameters for the planning target volumes (PTVs) and organs at risk (OAR) were compared. The experimental in vitro databases for the various models differed greatly in the range of (α/β) values and dose-averaged LET (LET). There were significant variations between the model estimations, which arose from fundamental differences in the database definitions and model assumptions. The greatest variations appeared in organs with low (α/β) and high LET, e.g. biological doses given to late responding OARs located distal to the target in the treatment field. In general, the variation in maximum dose (D) was larger than the variation in mean dose and other dose metrics, with D of the left optic nerve ((α/β) = 2.1 Gy) in the pituitary adenoma case showing the greatest discrepancies between models: 28-52 Gy(RBE), while D for RBE was 30 Gy(RBE). For all patient cases, the estimated mean RBE to the PTV was in the range 1.09-1.29 ((α/β) = 1.5/3.1/10.6 Gy). There were considerable variations between the estimations of RBE and RBE-weighted doses from the different models. These variations were a consequence of fundamental differences in experimental databases, model assumptions and regression techniques. The results from the implementation of RBE models in dose planning studies should be evaluated in light of these deviations.
质子的相对生物效应（RBE）受多种物理和生物学因素的影响。已经开发出了唯象 RBE 模型，以便在估计可变 RBE 时纳入这些因素，而不是采用临床应用的 1.1 恒定 RBE。在这项研究中，探索并应用了十一个已发表的唯象 RBE 模型和两个基于计划的模型来模拟患者病例。所有模型均根据其各自实验数据库的线性能量传递（LET）分布和范围以及参考辐射分割敏感性（（α/β））进行了分析。在 Eclipse 治疗计划系统中，使用 1.1 的 RBE 对水的扩展布拉格峰和三个患者病例（前列腺腺癌、垂体腺瘤和胸肉瘤）的质子治疗计划进行了优化，然后在 FLUKA 蒙特卡罗代码中重新计算和建模。比较了计划靶区（PTV）和危及器官（OAR）的模型估计剂量-体积参数。各种模型的实验体外数据库在（α/β）值和剂量平均 LET（LET）范围上存在很大差异。由于数据库定义和模型假设的根本差异，模型估计之间存在显着差异。最大的变化出现在（α/β）值低且 LET 高的器官中，例如位于靶区远端治疗场中的晚期反应 OAR 的生物剂量。一般来说，最大剂量（D）的变化大于平均剂量和其他剂量指标的变化，垂体腺瘤病例中左侧视神经的 D（（α/β）= 2.1 Gy）显示出模型之间最大的差异：28-52 Gy（RBE），而 RBE 的 D 为 30 Gy（RBE）。对于所有患者病例，PTV 的估计平均 RBE 在 1.09-1.29 范围内（（α/β）= 1.5/3.1/10.6 Gy）。不同模型对 RBE 和 RBE 加权剂量的估计存在很大差异。这些差异是实验数据库、模型假设和回归技术根本差异的结果。应该根据这些偏差来评估在剂量规划研究中实施 RBE 模型的结果。
