Sharma Mayur, Bennett Elizabeth E, Rahmathulla Gazanfar, Chao Samuel T, Koech Hilary K, Gregory Stephanie N, Emch Todd, Magnelli Anthony, Meola Antonio, Suh John H, Angelov Lilyana
Departments of 1 Neurosurgery and.
Department of Neurosurgery, University of Florida, Jacksonville, Florida.
Neurosurg Focus. 2017 Jan;42(1):E14. doi: 10.3171/2016.10.FOCUS16364.
OBJECTIVE Stereotactic radiosurgery (SRS) of the spine is a conformal method of delivering a high radiation dose to a target in a single or few (usually ≤ 5) fractions with a sharp fall-off outside the target volume. Although efforts have been focused on evaluating spinal cord tolerance when treating spinal column metastases, no study has formally evaluated toxicity to the surrounding organs at risk (OAR), such as the brachial plexus or the oropharynx, when performing SRS in the cervicothoracic region. The aim of this study was to evaluate the radiation dosimetry and the acute and delayed toxicities of SRS on OAR in such patients. METHODS Fifty-six consecutive patients (60 procedures) with a cervicothoracic spine tumor involving segments within C5-T1 who were treated using single-fraction SRS between February 2006 and July 2014 were included in the study. Each patient underwent CT simulation and high-definition MRI before treatment. The clinical target volume and OAR were contoured on BrainScan and iPlan software after image fusion. Radiation toxicity was evaluated using the common toxicity criteria for adverse events and correlated to the radiation doses delivered to these regions. The incidence of vertebral body compression fracture (VCF) before and after SRS was evaluated also. RESULTS Metastatic lesions constituted the majority (n = 52 [93%]) of tumors treated with SRS. Each patient was treated with a median single prescription dose of 16 Gy to the target. The median percentage of tumor covered by SRS was 93% (maximum target dose 18.21 Gy). The brachial plexus received the highest mean maximum dose of 17 Gy, followed by the esophagus (13.8 Gy) and spinal cord (13 Gy). A total of 14 toxicities were encountered in 56 patients (25%) during the study period. Overall, 14% (n = 8) of the patients had Grade 1 toxicity, 9% (n = 5) had Grade 2 toxicity, 2% (n = 1) had Grade 3 toxicity, and none of the patients had Grade 4 or 5 toxicity. The most common (12%) toxicity was dysphagia/odynophagia, followed by axial spine pain flare or painful radiculopathy (9%). The maximum radiation dose to the brachial plexus showed a trend toward significance (p = 0.066) in patients with worsening post-SRS pain. De novo and progressive VCFs after SRS were noted in 3% (3 of 98) and 4% (4 of 98) of vertebral segments, respectively. CONCLUSIONS From the analysis, the current SRS doses used at the Cleveland Clinic seem safe and well tolerated at the cervicothoracic junction. These preliminary data provide tolerance benchmarks for OAR in this region. Because the effect of dose-escalation SRS strategies aimed at improving local tumor control needs to be balanced carefully with associated treatment-related toxicity on adjacent OAR, larger prospective studies using such approaches are needed.
目的 脊柱立体定向放射外科（SRS）是一种适形放疗方法，可在单次或少数几次（通常≤5次）分割中将高剂量辐射精准投照至靶区，靶区外剂量迅速下降。尽管在治疗脊柱转移瘤时，人们一直致力于评估脊髓耐受性，但在颈胸段进行SRS时，尚无研究正式评估其对周围危及器官（OAR）如臂丛神经或口咽的毒性。本研究旨在评估此类患者SRS对OAR的放射剂量学以及急性和迟发性毒性。方法 纳入2006年2月至2014年7月间接受单次分割SRS治疗的56例连续患者（60例手术），其颈胸椎肿瘤累及C5 - T1节段。每位患者在治疗前均接受CT模拟和高清MRI检查。图像融合后，在BrainScan和iPlan软件上勾画临床靶区和OAR。使用不良事件通用毒性标准评估放射毒性，并将其与这些区域所接受的放射剂量相关联。同时评估SRS前后椎体压缩骨折（VCF）的发生率。结果 SRS治疗的肿瘤中，转移性病变占大多数（n = 52 [93%]）。每位患者靶区的中位单次处方剂量为16 Gy。SRS覆盖肿瘤的中位百分比为93%（最大靶剂量18.21 Gy）。臂丛神经接受的平均最大剂量最高，为17 Gy，其次是食管（13.8 Gy）和脊髓（13 Gy）。研究期间，56例患者（25%）共出现14例毒性反应。总体而言，14%（n = 8）的患者为1级毒性，9%（n = 5）为2级毒性，2%（n = 1）为3级毒性，无患者出现4级或5级毒性。最常见的毒性反应（12%）是吞咽困难/吞咽痛，其次是脊柱轴向疼痛加剧或神经根性疼痛（9%）。SRS后疼痛加重的患者中，臂丛神经的最大放射剂量显示出有统计学意义的趋势（p = 0.066）。SRS后新发和进行性VCF分别在3%（98个椎体节段中的3个）和4%（98个椎体节段中的4个）的椎体节段中被发现。结论 通过分析，克利夫兰诊所目前使用的SRS剂量在颈胸交界处似乎是安全且耐受性良好的。这些初步数据为此区域的OAR提供了耐受性基准。由于旨在改善局部肿瘤控制的剂量递增SRS策略的效果需要与对相邻OAR的相关治疗毒性仔细权衡，因此需要使用此类方法进行更大规模的前瞻性研究。
