Zheng Dandan, Yoon Jihyung, Jung Hyunuk, Lemus Olga Maria Dona, Gou Lang, Zhou Yuwei, Usuki Kenneth Y, Hardy Sara, Milano Michael T
Department of Radiation Oncology, University of Rochester Medical Center, Rochester, New York.
Adv Radiat Oncol. 2024 Mar 19;9(6):101499. doi: 10.1016/j.adro.2024.101499. eCollection 2024 Jun.
To investigate the relationship between normal brain exposure in LINAC-based single-isocenter multitarget multifraction stereotactic radiosurgery or stereotactic radiation therapy (SRT) and the number or volume of treated brain metastases, especially for high numbers of metastases.
A cohort of 44 SRT patients with 709 brain metastases was studied. Renormalizing to a uniform prescription of 27 Gy in 3 fractions, normal brain dose volume indices, including V23 Gy (volume receiving >23 Gy), V18 Gy (volume receiving >18 Gy), and mean dose, were evaluated on these plans against the number and the total volume of targets for each plan. To compare with exposures from whole-brain radiation therapy (WBRT), the SRT dose distributions were converted to equivalent dose in 3 Gy fractions (EQD3) using an alpha-beta ratio of 2 Gy.
With increasing number of targets and increasing total target volume, normal brain exposures to dose ≥18 Gy increases, and so does the mean normal brain dose. The factors of the number of targets and the total target volume are both significant, although the number of targets has a larger effect on the mean normal brain dose and the total target volume has a larger effect on V23 Gy and V18 Gy. The EQD3 mean normal brain dose with SRT planning is lower than conventional WBRT. On the other hand, SRT results in higher hot spot (ie, maximum dose outside of tumor) EQD3 dose than WBRT.
Based on clinical SRT plans, our study provides information on correlations between normal brain exposure and the number and total volume of targets. As SRT becomes more greatly used for patients with increasingly extensive brain metastases, more clinical data on outcomes and toxicities is necessary to better define the normal brain dose constraints for high-exposure cases and to optimize the SRT management for those patients.
探讨基于直线加速器的单等中心多靶点多分次立体定向放射外科或立体定向放射治疗（SRT）中正常脑暴露与治疗的脑转移瘤数量或体积之间的关系，尤其是对于大量转移瘤的情况。
对44例接受SRT治疗且有709个脑转移瘤的患者进行了队列研究。将这些计划重新归一化为3分次给予27 Gy的统一处方剂量，根据每个计划的靶点数量和总体积，评估正常脑剂量体积指数，包括V23 Gy（接受>23 Gy剂量的体积）、V18 Gy（接受>18 Gy剂量的体积）和平均剂量。为了与全脑放射治疗（WBRT）的暴露情况进行比较，使用2 Gy的α/β比值将SRT剂量分布转换为3 Gy分次的等效剂量（EQD3）。
随着靶点数量增加和总靶体积增大，正常脑接受≥18 Gy剂量的暴露增加，正常脑平均剂量也增加。靶点数量和总靶体积这两个因素均具有显著性，尽管靶点数量对正常脑平均剂量的影响更大，而总靶体积对V23 Gy和V18 Gy的影响更大。SRT计划的EQD3正常脑平均剂量低于传统WBRT。另一方面，SRT导致的热点（即肿瘤外的最大剂量）EQD3剂量高于WBRT。
基于临床SRT计划，我们的研究提供了正常脑暴露与靶点数量和总体积之间相关性的信息。随着SRT越来越多地用于脑转移瘤日益广泛的患者，需要更多关于疗效和毒性的临床数据，以更好地确定高暴露病例的正常脑剂量限制，并优化这些患者的SRT管理。
