Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, ON, Canada.
Int J Radiat Oncol Biol Phys. 2013 Feb 1;85(2):341-7. doi: 10.1016/j.ijrobp.2012.05.007. Epub 2012 Jun 17.
Dose-volume histogram (DVH) results for 9 cases of post spine stereotactic body radiation therapy (SBRT) radiation myelopathy (RM) are reported and compared with a cohort of 66 spine SBRT patients without RM.
DVH data were centrally analyzed according to the thecal sac point maximum (Pmax) volume, 0.1- to 1-cc volumes in increments of 0.1 cc, and to the 2 cc volume. 2-Gy biologically equivalent doses (nBED) were calculated using an α/β = 2 Gy (units = Gy(2/2)). For the 2 cohorts, the nBED means and distributions were compared using the t test and Mann-Whitney test, respectively. Significance (P<.05) was defined as concordance of both tests at each specified volume. A logistic regression model was developed to estimate the probability of RM using the dose distribution for a given volume.
Significant differences in both the means and distributions at the Pmax and up to the 0.8-cc volume were observed. Concordant significance was greatest for the Pmax volume. At the Pmax volume the fit of the logistic regression model, summarized by the area under the curve, was 0.87. A risk of RM of 5% or less was observed when limiting the thecal sac Pmax volume doses to 12.4 Gy in a single fraction, 17.0 Gy in 2 fractions, 20.3 Gy in 3 fractions, 23.0 Gy in 4 fractions, and 25.3 Gy in 5 fractions.
We report the first logistic regression model yielding estimates for the probability of human RM specific to SBRT.
报告 9 例脊柱立体定向体部放射治疗（SBRT）后放射性脊髓病（RM）的剂量-体积直方图（DVH）结果，并与 66 例无 RM 的脊柱 SBRT 患者队列进行比较。
根据硬脊膜囊点最大（Pmax）体积、0.1-1cc 体积以 0.1cc 递增以及 2cc 体积，对 DVH 数据进行中心分析。采用α/β=2Gy（单位：Gy(2/2)）计算 2Gy 生物等效剂量（nBED）。对于这两个队列，使用 t 检验和 Mann-Whitney 检验分别比较 nBED 平均值和分布。在每个指定体积下，当两个检验结果一致时定义为有统计学意义（P<.05）。采用逻辑回归模型，根据特定体积的剂量分布，估算 RM 的概率。
在 Pmax 及 0.8-cc 体积范围内，观察到平均值和分布均有显著差异。Pmax 体积的一致性最为显著。在 Pmax 体积处，逻辑回归模型的拟合优度（曲线下面积）为 0.87。当限制硬脊膜囊 Pmax 体积剂量在单次分割时为 12.4Gy，2 次分割时为 17.0Gy，3 次分割时为 20.3Gy，4 次分割时为 23.0Gy，5 次分割时为 25.3Gy，观察到 RM 风险为 5%或更低。
我们报告了第一个用于预测 SBRT 特定的人类 RM 概率的逻辑回归模型。
