Sgouros George, Knox Susan J, Joiner Michael C, Morgan William F, Kassis Amin I
School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
J Nucl Med. 2007 Oct;48(10):1683-91. doi: 10.2967/jnumed.105.028183. Epub 2007 Sep 14.
Bystander and low-dose-rate effects influence the dose-response relationship in a manner not predicted by current dosimetric methodologies. Radiation-induced bystander effects refer to biologic responses in cells that are not traversed by an ionizing radiation track and, thus, not subject to direct energy deposition; that is, the responses occur in nonirradiated cells. Low-dose-rate hypersensitivity effects have been documented as a reduction in the survival of cells irradiated at dose rates of 0.1-1.0 Gy/h, with total doses ranging from 1.5 to 5 Gy. For humans undergoing external radiotherapy, evidence of bystander events has been observed in the form of abscopal effects, wherein irradiation of one portion of the anatomy affects a portion outside the radiation field, whereas low-dose-rate hypersensitivity has not been described. In this report, the historical literature is briefly reviewed, key experiments are summarized, and current understanding of the factors thought to be involved in the bystander and low-dose-rate effects is conveyed. The mechanisms associated with these events are still being investigated, and questions remain on their impact in radionuclide therapy. Although current findings do not yet sufficiently justify changing traditional dose estimates used to predict the outcomes of radionuclide therapy, it is important to appreciate the potential importance of these effects and to begin revising methods to reflect the emerging empiric and mechanistic knowledge.
旁观者效应和低剂量率效应会以当前剂量测定方法无法预测的方式影响剂量反应关系。辐射诱导的旁观者效应是指未被电离辐射径迹穿过因而未经历直接能量沉积的细胞中的生物学反应；也就是说，这些反应发生在未受照射的细胞中。低剂量率超敏效应已被记录为细胞在0.1 - 1.0 Gy/h的剂量率下接受照射时存活率降低，总剂量范围为1.5至5 Gy。对于接受外部放射治疗的人类，已观察到旁观者事件的证据，表现为远隔效应，即身体某一部分受到照射会影响辐射野外的另一部分，而低剂量率超敏效应尚未见报道。在本报告中，简要回顾了历史文献，总结了关键实验，并阐述了目前对被认为与旁观者效应和低剂量率效应相关的因素的理解。与这些事件相关的机制仍在研究中，关于它们在放射性核素治疗中的影响也存在疑问。尽管目前的研究结果尚未充分证明有必要改变用于预测放射性核素治疗结果的传统剂量估计，但认识到这些效应的潜在重要性并开始修订方法以反映新出现的经验和机制知识是很重要的。
