Hatiboglu Mustafa Aziz, Akdur Kerime
Department of Neurosurgery, Bezmialem Vakif University Medical School, Istanbul, Turkey.
Stereotact Funct Neurosurg. 2017;95(4):268-278. doi: 10.1159/000478272. Epub 2017 Aug 16.
Treatment of patients with multiple brain metastases has shifted to stereotactic radiosurgery, withholding whole-brain (WB) radiation therapy. However, radiation toxicity to the brain is a concern when treating multiple brain lesions with single-fraction stereotactic radiosurgery.
The purpose of this study was to determine the changes in brain radiation doses when treating various numbers of targets and lesion volumes.
We simulated different treatment plans with different combinations of varying tumor volumes including 0.1, 0.5, 1, 2, and 5 cm3, and tumor numbers including 1, 3, 5, 10, 15, 20, and 25. Treatment planning was performed for all combinations in a computerized tomography of the head of a patient, using Leksell GammaPlan version 10.1.1 (Elekta AB, Stockholm, Sweden). Two different dosing strategies were used. In the lower-prescription dosing schedule, a marginal dose was given to the 50% isodose line, and 20 Gy were used when the number of lesions was less than 15 and 18 Gy were applied when the number of lesions was equal to or more than 15. In the higher-prescription dosing schedule, a marginal dose of 24 Gy was used for lesions of less than 5 cm3 and 20 Gy were applied for lesions equal to 5cm3. The mean WB dose, the WB integral dose, and the volume of brain receiving 12 Gy (V12 Gy) were calculated for each scenario. Also, the beam-on time of the Gamma Knife 4C unit was reported for all treatment scenarios.
Regression analysis showed that the total tumor volume was a more significant predictor of V12 Gy than the number of lesions, and a linear correlation between the total tumor volume and V12 Gy was found. We also found that the total tumor volume was a more significant predictor of the mean WB dose and the WB integral dose compared to the number of lesions.
Our results suggest that multiple small to mid-sized lesions could be safely treated with a single-fraction gamma knife.
多脑转移瘤患者的治疗已转向立体定向放射外科，不再进行全脑放疗。然而，在用单次分割立体定向放射外科治疗多个脑病灶时，脑辐射毒性是一个令人担忧的问题。
本研究的目的是确定治疗不同数量的靶点和病灶体积时脑辐射剂量的变化。
我们模拟了不同的治疗计划，这些计划具有不同的肿瘤体积组合，包括0.1、0.5、1、2和5 cm³，以及不同的肿瘤数量，包括1、3、5、10、15、20和25。使用Leksell GammaPlan版本10.1.1（瑞典斯德哥尔摩的Elekta AB公司）在一名患者头部的计算机断层扫描中对所有组合进行治疗计划。采用了两种不同的给药策略。在低处方给药方案中，对50%等剂量线给予边缘剂量，当病灶数量少于15个时使用20 Gy，当病灶数量等于或多于15个时使用18 Gy。在高处方给药方案中，对于小于5 cm³的病灶使用24 Gy的边缘剂量，对于等于5 cm³的病灶使用20 Gy。计算每种情况下的平均全脑剂量、全脑积分剂量以及接受12 Gy（V12 Gy）的脑体积。此外，还报告了所有治疗方案中伽玛刀4C单元的照射时间。
回归分析表明，总肿瘤体积比病灶数量更能显著预测V12 Gy，并且发现总肿瘤体积与V12 Gy之间存在线性相关性。我们还发现，与病灶数量相比，总肿瘤体积更能显著预测平均全脑剂量和全脑积分剂量。
我们的结果表明，多个中小尺寸病灶可以安全地用单次分割伽玛刀治疗。
