Yang Hao, Cai Bo-ning, Wang Xiao-shen, Cong Xiao-hu, Xu Wei, Wang Jin-yuan, Yang Jun, Xu Shou-ping, Ju Zhong-jian, Ma Lin
Department of Radiation Oncology, Chinese PLA General Hospital, Beijing, China (mainland).
Department of Oncology, First Affiliated Hospital of Xinxiang Medical University, Weihui, Henan, China (mainland).
Med Sci Monit. 2016 Feb 23;22:598-607. doi: 10.12659/msm.897146.
BACKGROUND This study investigated and quantified the dosimetric impact of the distance from the tumor to the spinal cord and fractionation schemes for patients who received stereotactic body radiation therapy (SBRT) and hypofractionated simultaneous integrated boost (HF-SIB). MATERIAL AND METHODS Six modified planning target volumes (PTVs) for 5 patients with spinal metastases were created by artificial uniform extension in the region of PTV adjacent spinal cord with a specified minimum tumor to cord distance (0-5 mm). The prescription dose (biologic equivalent dose, BED) was 70 Gy in different fractionation schemes (1, 3, 5, and 10 fractions). For PTV V100, Dmin, D98, D95, and D1, spinal cord dose, conformity index (CI), V30 were measured and compared. RESULTS PTV-to-cord distance influenced PTV V100, Dmin, D98, and D95, and fractionation schemes influenced Dmin and D98, with a significant difference. Distances of ≥2 mm, ≥1 mm, ≥1 mm, and ≥0 mm from PTV to spinal cord meet dose requirements in 1, 3, 5, and 10 fractionations, respectively. Spinal cord dose, CI, and V30 were not impacted by PTV-to-cord distance and fractionation schemes. CONCLUSIONS Target volume coverage, Dmin, D98, and D95 were directly correlated with distance from the spinal cord for spine SBRT and HF-SIB. Based on our study, ≥2 mm, ≥1 mm, ≥1 mm, and ≥0 mm distance from PTV to spinal cord meets dose requirements in 1, 3, 5 and 10 fractionations, respectively.
背景 本研究调查并量化了接受立体定向体部放射治疗（SBRT）和超分割同步整合加量（HF-SIB）的患者中肿瘤与脊髓距离以及分割方案的剂量学影响。
材料与方法 对5例脊柱转移瘤患者，通过在PTV邻近脊髓区域人工均匀扩展，创建6个修改后的计划靶体积（PTV），设定肿瘤与脊髓的最小距离为0至5毫米。在不同分割方案（1、3、5和10次分割）下，处方剂量（生物等效剂量，BED）为70 Gy。测量并比较PTV的V100、Dmin、D98、D95和D1、脊髓剂量、适形指数（CI）、V30。
结果 PTV与脊髓的距离影响PTV的V100、Dmin、D98和D95，分割方案影响Dmin和D98，差异有统计学意义。PTV与脊髓距离≥2毫米、≥1毫米、≥1毫米和≥0毫米分别在1、3、5和10次分割时满足剂量要求。脊髓剂量、CI和V30不受PTV与脊髓距离及分割方案的影响。
结论 对于脊柱SBRT和HF-SIB，靶区体积覆盖、Dmin、D98和D95与脊髓距离直接相关。根据我们的研究，PTV与脊髓距离≥2毫米、≥1毫米、≥1毫米和≥0毫米分别在1、3、5和10次分割时满足剂量要求。
