Radiobiology of hypofractionated stereotactic radiotherapy: what are the optimal fractionation schedules?
Radiobiology of hypofractionated stereotactic radiotherapy: what are the optimal fractionation schedules?
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DOI：
10.1093/jrr/rrw015
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发表时间：
2016-08
影响因子：
2
通讯作者：
Iwata H
中科院分区：
文献类型：
--
作者：
Shibamoto Y;Miyakawa A;Otsuka S;Iwata H
在大分割立体定向放射治疗（SRT）中，每次分割通常使用高剂量，并且剂量输送模式与常规放射不同。与常规放射治疗相比，每日剂量通常在较长时间内间歇给予。在长时间的辐射传递过程中，发生亚致死损伤修复，导致辐射效应降低。然而，在体内肿瘤中，这种效果的降低可以通过快速复氧来抵消。与大分割SRT相关的另一个问题是剂量评估和转换的数学模型。线性二次（LQ）模型和生物有效剂量（BED）已被认为是不正确的，当用于低分割。LQ模型高估了高剂量辐射的影响。当用于体内肿瘤反应时，BED尤其不正确，因为它没有考虑再氧合。当将BED用于SRT时，需要校正与BED使用相关的误差（估计为5- 20%）。据报道，高分数剂量表现出对肿瘤血管系统的作用，并增强宿主免疫力，导致抗肿瘤作用增加。这可能是一个值得进一步研究的有趣话题。低氧肿瘤细胞的放射抗性在低分次SRT中更成问题，因此未来鼓励进行低氧靶向药物的试验。本文总结了大分割SRT的放射生物学特性，并基于此考虑，建议对直径大于2 cm的肺肿瘤采用60戈伊，分8次，每周3次。
In hypofractionated stereotactic radiotherapy (SRT), high doses per fraction are usually used and the dose delivery pattern is different from that of conventional radiation. The daily dose is usually given intermittently over a longer time compared with conventional radiotherapy. During prolonged radiation delivery, sublethal damage repair takes place, leading to the decreased effect of radiation. In in vivo tumors, however, this decrease in effect may be counterbalanced by rapid reoxygenation. Another issue related to hypofractionated SRT is the mathematical model for dose evaluation and conversion. The linear–quadratic (LQ) model and biologically effective dose (BED) have been suggested to be incorrect when used for hypofractionation. The LQ model overestimates the effect of high fractional doses of radiation. BED is particularly incorrect when used for tumor responses in vivo, since it does not take reoxygenation into account. Correction of the errors, estimated at 5–20%, associated with the use of BED is necessary when it is used for SRT. High fractional doses have been reported to exhibit effects against tumor vasculature and enhance host immunity, leading to increased antitumor effects. This may be an interesting topic that should be further investigated. Radioresistance of hypoxic tumor cells is more problematic in hypofractionated SRT, so trials of hypoxia-targeted agents are encouraged in the future. In this review, the radiobiological characteristics of hypofractionated SRT are summarized, and based on the considerations, we would like to recommend 60 Gy in eight fractions delivered three times a week for lung tumors larger than 2 cm in diameter.
影响因子：
8.8
作者：
Shibamoto, Y;Ohshio, G;Hosotani, R;Nishimura, Y;Manabe, T;Imamura, M;Abe, M
通讯作者：
Abe, M