Noble D J, Ajithkumar T, Lambert J, Gleeson I, Williams M V, Jefferies S J
Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK; Department of Oncology, Cambridge University Hospital's NHS Foundation Trust, Cambridge, UK.
Department of Oncology, Cambridge University Hospital's NHS Foundation Trust, Cambridge, UK.
Clin Oncol (R Coll Radiol). 2017 Jul;29(7):439-447. doi: 10.1016/j.clon.2017.02.013. Epub 2017 Mar 18.
Craniospinal irradiation (CSI) remains a crucial treatment for patients with medulloblastoma. There is uncertainty about how to manage meningeal surfaces and cerebrospinal fluid (CSF) that follows cranial nerves exiting skull base foramina. The purpose of this study was to assess plan quality and dose coverage of posterior cranial fossa foramina with both photon and proton therapy.
We analysed the radiotherapy plans of seven patients treated with CSI for medulloblastoma and primitive neuro-ectodermal tumours and three with ependymoma (total n = 10). Four had been treated with a field-based technique and six with TomoTherapy™. The internal acoustic meatus (IAM), jugular foramen (JF) and hypoglossal canal (HC) were contoured and added to the original treatment clinical target volume (Plan_CTV) to create a Test_CTV. This was grown to a test planning target volume (Test_PTV) for comparison with a Plan_PTV. Using Plan_CTV and Plan_PTV, proton plans were generated for all 10 cases. The following dosimetry data were recorded: conformity (dice similarity coefficient) and homogeneity index (D - D/D) as well as median and maximum dose (D) to Plan_PTV, V and minimum dose (D) to Plan_CTV and Test_CTV and Plan_PTV and Test_PTV, V and minimum dose (D) to foramina PTVs.
Proton and TomoTherapy™ plans were more conformal (0.87, 0.86) and homogeneous (0.07, 0.04) than field-photon plans (0.79, 0.17). However, field-photon plans covered the IAM, JF and HC PTVs better than proton plans (P = 0.002, 0.004, 0.003, respectively). TomoTherapy™ plans covered the IAM and JF better than proton plans (P = 0.000, 0.002, respectively) but the result for the HC was not significant. Adding foramen CTVs/PTVs made no difference for field plans. The mean D dropped 3.4% from Plan_PTV to Test_PTV for TomoTherapy™ (not significant) and 14.8% for protons (P = 0.001).
Highly conformal CSI techniques may underdose meninges and CSF in the dural reflections of posterior fossa cranial nerves unless these structures are specifically included in the CTV.
对于髓母细胞瘤患者，颅脊髓照射（CSI）仍是一种关键的治疗方法。对于如何处理脑膜表面以及沿穿出颅底孔的颅神经走行的脑脊液（CSF），目前尚存在不确定性。本研究的目的是评估光子和质子治疗对后颅窝孔的计划质量和剂量覆盖情况。
我们分析了7例接受CSI治疗的髓母细胞瘤和原始神经外胚层肿瘤患者以及3例室管膜瘤患者（共10例）的放射治疗计划。4例采用基于野的技术治疗，6例采用螺旋断层放疗（TomoTherapy™）治疗。勾勒出内耳道（IAM）、颈静脉孔（JF）和舌下神经管（HC），并将其添加到原始治疗临床靶区（Plan_CTV）中，以创建测试临床靶区（Test_CTV）。将其扩展为测试计划靶区（Test_PTV），以便与计划计划靶区（Plan_PTV）进行比较。利用Plan_CTV和Plan_PTV，为所有10例患者生成质子计划。记录以下剂量学数据：适形性（骰子相似系数）和均匀性指数（D - D/D），以及Plan_PTV的中位剂量和最大剂量（D）、Plan_CTV和Test_CTV以及Plan_PTV和Test_PTV的V以及孔道计划靶区的最小剂量（D）。
质子和螺旋断层放疗（TomoTherapy™）计划比基于野的光子计划更适形（0.87，0.86）和均匀（0.07，0.04）（分别为0.79，0.17）。然而，基于野的光子计划对IAM、JF和HC计划靶区的覆盖优于质子计划（分别为P = 0.002、0.004、0.003）。螺旋断层放疗（TomoTherapy™）计划对IAM和JF的覆盖优于质子计划（分别为P = 0.000、0.002），但对HC的结果无统计学意义。添加孔道临床靶区/计划靶区对基于野的计划无影响。对于螺旋断层放疗（TomoTherapy™），从Plan_PTV到Test_PTV的平均D下降了3.4%（无统计学意义），对于质子下降了14.8%（P = 0.001）。
除非这些结构被特意纳入临床靶区，否则高度适形的CSI技术可能会使后颅窝颅神经硬脑膜反射处的脑膜和脑脊液剂量不足。
