Owen Dawn, Mayo Charles S, Song Limin, Ahmed Kamran, Laack Nadia, Olivier Kenneth
Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
Department of Radiation Oncology, Mayo Clinic Rochester, Rochester, Minnesota.
Adv Radiat Oncol. 2015 Dec 19;1(1):76-81. doi: 10.1016/j.adro.2015.12.001. eCollection 2016 Jan-Mar.
Spine stereotactic body radiation therapy (SBRT) is becoming widely accepted as first-line treatment of oligometastatic spine disease as well as in the postoperative setting. The reported incidence of myelopathy is very low and guidelines vary widely on the maximum tolerable dose of the spinal cord and thecal sac.
Between April 2008 and December 2010, radiation parameters were exported for 46 patients treated with spine SBRT at the Mayo Clinic. Using an in-house data mining program, dose-volume histogram constraints were extracted, including dose prescription, dose fractionation, planning target volume, planning target volume coverage, maximum dose to the cord, D2cc thecal sac, and D2cc spinal cord. Diagnostic magnetic resonance imaging scans and/or computed tomography myelograms were fused with the planning set to delineate the cord and thecal sac for receiver operating characteristic analysis of cord and thecal sac subvolume doses. A high-resolution planning at-risk volume was created in 1-mm increments for cord (1-7 mm) and the thecal sac (1-2 mm) to examine dose gradients that might be correlated with toxicity.
No patients experienced myelopathy with a median follow-up of 14 months. The most common toxicities were pain and nausea. Median values of D2cc maximum dose (maximum dose received by 2 cc of the organ at risk; biologically equivalent 2-Gy dose maximum [EQD2]) for cord and thecal sac were 38.5 Gy (range, 7.5-67.9 Gy) and 67.7 Gy (range, 15.5-155.8 Gy), respectively. Median values for high-dose subvolumes for cord and thecal sac were 2 times higher than the doses for 5% predicted grade 3 cord toxicity as recommended in the current literature. Cord D0.1cc[EQD2] ≥23.8 Gy was correlated with pain flare (n = 5). Thecal sac D2cc [EQD2] ≥29.3 Gy was a significant indicator of nausea.
Current guidelines may overestimate the risk of myelopathy from spine SBRT. The current study's population included both radiation-naïve and retreatment cases, but no myelopathy was observed despite exceeding recommended spine limits.
脊柱立体定向体部放射治疗（SBRT）作为寡转移脊柱疾病的一线治疗方法以及术后治疗方法正被广泛接受。报道的脊髓病发病率非常低，并且关于脊髓和硬膜囊的最大耐受剂量的指南差异很大。
2008年4月至2010年12月期间，导出了梅奥诊所46例接受脊柱SBRT治疗患者的放射参数。使用内部数据挖掘程序，提取剂量体积直方图约束条件，包括剂量处方、剂量分割、计划靶体积、计划靶体积覆盖率、脊髓最大剂量、2cc硬膜囊剂量和2cc脊髓剂量。将诊断性磁共振成像扫描和/或计算机断层脊髓造影与计划数据集融合，以勾勒脊髓和硬膜囊，用于脊髓和硬膜囊亚体积剂量的受试者操作特征分析。以1mm的增量为脊髓（1 - 7mm）和硬膜囊（1 - 2mm）创建高分辨率计划危险体积，以检查可能与毒性相关的剂量梯度。
中位随访14个月，无患者发生脊髓病。最常见的毒性反应是疼痛和恶心。脊髓和硬膜囊的2cc最大剂量（危险器官2cc接受的最大剂量；生物等效2 - Gy剂量最大值[EQD2]）的中位值分别为38.5 Gy（范围7.5 - 67.9 Gy）和67.7 Gy（范围15.5 - 155.8 Gy）。脊髓和硬膜囊高剂量亚体积的中位值比当前文献中推荐的5%预测3级脊髓毒性剂量高2倍。脊髓D0.1cc[EQD2]≥23.8 Gy与疼痛发作相关（n = 5）。硬膜囊D2cc [EQD2]≥29.3 Gy是恶心的重要指标。
当前指南可能高估了脊柱SBRT导致脊髓病的风险。本研究人群包括初次放疗和再治疗病例，但尽管超过了推荐的脊柱剂量限制，仍未观察到脊髓病。
