Xue Jinyu, LaCouture Tamara, Grimm Jimm, Goldman H Warren, Ibbott Geoffrey S, Yorke Ellen, Kubicek Gregory J
Department of Radiation Oncology, MD Anderson Cancer Center at Cooper, Camden, NJ 08103, USA.
Holy Redeemer Hospital, Meadowbrook, PA, 19046, USA.
J Radiosurg SBRT. 2015;3(4):271-279.
Treatment option of stereotactic radiosurgery versus whole brain radiotherapy for multiple brain metastases (>10) is an ongoing debate. Detailed dosimetric and biological information are presented in this study to investigate the possible clinical outcomes.Materials and Methods: Nine patients with multiple brain metastases (11-25) underwent stereotactic radiosurgery. Whole brain radiotherapy plans are retrospectively designed with the same MR image set and the same structure set for each patient using the standard opposing lateral beams and fractionation (3 Gy × 10).Physical doses and biologically effective doses are calculated for each lesion target and the CNS normal tissues and they are compared between whole brain radiotherapy and stereotactic radiosurgery in the context of clinical efficacy and published toxicities.
Tumor biologically effective dose is higher in radiosurgery than in whole brain radiotherapy by factors of 3.2-5.3 in maximum dose and of 2.4-3.1 in mean dose. Biologically effective mean dose in radiosurgery is 1.3-34.3% for normal brain, 0.7-31.6% for brainstem, 0.5-5.7% for chiasm, 0.2-5.7% for optic nerves and 0.6-18.1% for hippocampus of that in whole brain radiotherapy over nine cases presented here. We also presented the dose-volume relationship for normal brain to address the dosimetric concerns in radiosurgery.
Dose-volume metrics presented in this study are essential to understanding the safety and efficacy of whole brain radiotherapy and/or radiosurgery for multiple brain metastases. Whole brain radiotherapy has resulted in higher incidence of radiation-related toxicities than radiosurgery. Even for patients with more than 10 brain metastases, the CNS normal tissues receive significantly lower doses in radiosurgery. Mean normal brain dose in SRS is found to correlate with the total volume of lesions rather than the number of lesions treated.
对于多发脑转移瘤（超过10个），立体定向放射外科治疗与全脑放疗的治疗选择一直存在争议。本研究提供详细的剂量学和生物学信息，以探究可能的临床结果。
9例多发脑转移瘤（11 - 25个）患者接受了立体定向放射外科治疗。使用标准的对侧野照射和分割方式（3 Gy×10），针对每位患者，利用相同的磁共振图像集和相同的结构集，回顾性设计全脑放疗计划。计算每个病灶靶区和中枢神经系统正常组织的物理剂量和生物等效剂量，并在临床疗效和已发表的毒性反应背景下，对全脑放疗和立体定向放射外科治疗进行比较。
在最大剂量方面，放射外科治疗的肿瘤生物等效剂量比全脑放疗高3.2 - 5.3倍，在平均剂量方面高2.4 - 3.1倍。在本研究呈现的9例病例中，放射外科治疗的正常脑、脑干、视交叉、视神经和海马的生物等效平均剂量分别是全脑放疗的1.3 - 百分之34.3、0.7 - 百分之31.6、0.5 - 百分之5.7、0.2 - 百分之5.7和0.6 - 百分之18.1。我们还展示了正常脑的剂量 - 体积关系，以解决放射外科治疗中的剂量学问题。
本研究中呈现的剂量 - 体积指标对于理解全脑放疗和/或立体定向放射外科治疗多发脑转移瘤的安全性和疗效至关重要。全脑放疗导致的放射性毒性发生率高于放射外科治疗。即使对于有超过10个脑转移瘤的患者，中枢神经系统正常组织在放射外科治疗中接受的剂量也显著更低。发现立体定向放射外科治疗中正常脑的平均剂量与病灶总体积相关，而非与治疗的病灶数量相关。
