PDF(Pubmed)
Abstract：
The standard of care for radiation therapy is numerous, low-dose fractions that are distributed homogeneously throughout the tumor. An alternative strategy under scrutiny is to apply spatially fractionated radiotherapy (high and low doses throughout the tumor) in one or several fractions, either alone or followed by conventional radiation fractionation . Spatial fractionation allows for significant sparing of normal tissue, and the regions of tumor or normal tissue that received sublethal doses can give rise to beneficial bystander effects in both cases. Bystander effects are broadly defined as biological responses that are significantly greater than would be anticipated based on the radiation dose received. Typically these effects are initiated by diffusion of reactive oxygen species and secretion of various cytokines. As demonstrated in the literature, spatial fractionation related bystander effects can occur locally from cell to cell and in what are known as \"cohort effects,\" which tend to take the form of restructuring of the vasculature, enhanced immune infiltration, and development of immunological memory. Other bystander effects can take place at distant sites in what are known as \"abscopal effects.\" While these events are rare, they are mediated by the immune system and can result in the eradication of secondary and metastatic disease. Currently, due to the complexity and variability of these bystander effects, they are not thoroughly understood, but as knowledge improves they may present significant opportunities for improved clinical outcomes.
摘要：
放射治疗的护理标准很多，在整个肿瘤中均匀分布的低剂量部分。正在审查的另一种策略是在一个或几个部分中应用空间分割的放射疗法（整个肿瘤的高剂量和低剂量），单独或随后进行常规辐射分馏。空间分割允许显著保留正常组织，在两种情况下，接受亚致死剂量的肿瘤或正常组织区域都会产生有益的旁观者效应。旁观者效应被广泛定义为生物反应，其明显大于基于所接收的辐射剂量的预期。通常,这些作用是通过活性氧的扩散和各种细胞因子的分泌引发的。正如文献中所证明的，空间分级分离相关的旁观者效应可以在细胞与细胞之间局部发生，在所谓的“队列效应”中，“倾向于采取脉管系统重组的形式，增强的免疫浸润，和免疫记忆的发展。其他旁观者效应可能发生在遥远的地方，这就是所谓的“abscopal效应”。“虽然这些事件很少见，它们是由免疫系统介导的，可以导致根除继发性和转移性疾病。目前,由于这些旁观者效应的复杂性和可变性，他们没有被彻底理解，但随着知识水平的提高,它们可能为改善临床结局提供重要机会.
