Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada.
Int J Radiat Oncol Biol Phys. 2012 Jan 1;82(1):107-16. doi: 10.1016/j.ijrobp.2010.08.021. Epub 2010 Oct 15.
We reviewed the treatment for patients with spine metastases who initially received conventional external beam radiation (EBRT) and were reirradiated with 1-5 fractions of stereotactic body radiotherapy (SBRT) who did or did not subsequently develop radiation myelopathy (RM).
Spinal cord dose-volume histograms (DVHs) for 5 RM patients (5 spinal segments) and 14 no-RM patients (16 spine segments) were based on thecal sac contours at retreatment. Dose to a point within the thecal sac that receives the maximum dose (P(max)), and doses to 0.1-, 1.0-, and 2.0-cc volumes within the thecal sac were reviewed. The biologically effective doses (BED) using α/β = 2 Gy for late spinal cord toxicity were calculated and normalized to a 2-Gy equivalent dose (nBED = Gy(2/2)).
The initial conventional radiotherapy nBED ranged from ~30 to 50 Gy(2/2) (median ~40 Gy(2/2)). The SBRT reirradiation thecal sac mean P(max) nBED in the no-RM group was 20.0 Gy(2/2) (95% confidence interval [CI], 10.8-29.2), which was significantly lower than the corresponding 67.4 Gy(2/2) (95% CI, 51.0-83.9) in the RM group. The mean total P(max) nBED in the no-RM group was 62.3 Gy(2/2) (95% CI, 50.3-74.3), which was significantly lower than the corresponding 105.8 Gy(2/2) (95% CI, 84.3-127.4) in the RM group. The fraction of the total P(max) nBED accounted for by the SBRT P(max) nBED for the RM patients ranged from 0.54 to 0.78 and that for the no-RM patients ranged from 0.04 to 0.53.
SBRT given at least 5 months after conventional palliative radiotherapy with a reirradiation thecal sac P(max) nBED of 20-25 Gy(2/2) appears to be safe provided the total P(max) nBED does not exceed approximately 70 Gy(2/2), and the SBRT thecal sac P(max) nBED comprises no more than approximately 50% of the total nBED.
我们回顾了最初接受常规外束放射治疗（EBRT）并随后接受 1-5 次立体定向体放射治疗（SBRT）再照射的脊柱转移瘤患者的治疗情况，这些患者随后是否发生放射性脊髓病（RM）。
5 例 RM 患者（5 个脊柱节段）和 14 例无 RM 患者（16 个脊柱节段）的脊髓剂量-体积直方图（DVH）基于再治疗时硬脊膜囊轮廓。我们回顾了硬脊膜囊内接受最大剂量的一点（P（max））的剂量，以及硬脊膜囊内 0.1、1.0 和 2.0 立方厘米体积的剂量。使用α/β = 2 Gy 计算晚期脊髓毒性的生物有效剂量（BED），并归一化为 2 Gy 等效剂量（nBED = Gy（2/2））。
初始常规放疗 nBED 范围为 30 至 50 Gy（2/2）（中位数 40 Gy（2/2））。无 RM 组 SBRT 再照射硬脊膜囊 P（max） nBED 平均值为 20.0 Gy（2/2）（95%置信区间 [CI]，10.8-29.2），明显低于 RM 组相应的 67.4 Gy（2/2）（95% CI，51.0-83.9）。无 RM 组的总 P（max） nBED 平均值为 62.3 Gy（2/2）（95% CI，50.3-74.3），明显低于 RM 组相应的 105.8 Gy（2/2）（95% CI，84.3-127.4）。RM 患者的总 P（max） nBED 中 SBRT P（max） nBED 所占的分数范围为 0.54 至 0.78，无 RM 患者的分数范围为 0.04 至 0.53。
在常规姑息性放疗后至少 5 个月给予 SBRT，再照射硬脊膜囊 P（max） nBED 为 20-25 Gy（2/2），只要总 P（max） nBED 不超过约 70 Gy（2/2），并且 SBRT 硬脊膜囊 P（max） nBED 不超过总 nBED 的 50%，似乎是安全的。
