儿童全脑全脊髓放疗SIOPE指南全脑靶区勾画临床应用研究

目的 根据SIOPE指南勾画全脑全脊髓放疗患者的全脑靶区,验证原计划中未勾画的亚结构欠量情况,为全脑全脊髓放疗儿童患者全脑复发风险的研究提供证据,同时为SIOPE指南全脑靶区勾画临床应用积累经验。方法 选择12例全脑全脊髓放疗的儿童患者,根据2018年SIOPE指南在原有全脑靶区CTVold (全脑组织加筛板)基础上增加勾画亚结构CTVsub (包括眶上裂、圆孔、卵圆孔、颈静脉孔、舌下神经管、内听道以及视神经),合并且外放形成PTVnew。在CTVold基础上往前下方向(颅底方向)外放15mm、其余方向外放3mm适当修改后形成简易PTV (PTVrough)。按照PTVold设计CRTold、IMRTold计划,按照PTVnew设计CRTnew、IMRTnew计划,按照PTVrough设计CRTrough计划。评估基于CTVold靶区的亚结构的遗漏及其基于各个计划的欠量情况。结果 若基于CTVold勾画,则有78.6%的眶上裂、71.99%的圆孔、96.76%的卵圆孔、88.5%的颈静脉孔、97.71%的舌下神经管、99.48%的内听道以及100%的视神经体积被遗漏。基于CRTold、IMRTold计划亚结构的处方剂量覆盖分别仅为91.70%、89.83%。基于CRTold、CRTnew、IMRTold、IMRTnew、CRTrough计划,分别有16.66%、3.57%、20.83%、1.78%、1.19%的亚结构发生欠量。在所有的亚结构欠量中,38.36%、46.58%的欠z量分别发生在CRTold、IMRTold计划中。其中欠量最少、最多的分别为圆孔(0%)、卵圆孔(36.66%)。结论 按照SIOPE指南,在全脑全脊髓放疗患者全脑靶区勾画时,传统的脑组织勾画(包括筛板)将会遗漏部分靶区并且会欠量,其中卵圆孔欠量最严重而在IMRT计划中遗漏靶区的欠量更明显;基于亚结构勾画的计划将明显改善其欠量情况;选择左右对穿照射技术时,采用简易PTV方法可以获得近似的靶区剂量覆盖和危及器官保护,但还需要临床的进一步验证。

Clinical application of SIOPE guidelines in target definition for craniospinal irradiation in children

Objective According to the SIOPE (2018) guidelines,the whole brain target of patients undergoing craniospinal irradiation was delineated and the underdose of sub-structures which were not delineated in original plan was verified, aiming to provide evidence for the risk of whole brain recurrence of craniospinal irradiation and accumulate experience for the clinical application of SIOPE guidelines. Methods Twelve children who underwent craniospinal irradiation were selected. As per the SIOPE guidelines in 2018, the CTVsub (including the superior orbital fissure,foramen rotundum,foramen ovale,jugular foramen,hypoglossal canal,internal auditory meatus and optic nerve) were delineated based on the original CTVold (whole brain plus sieve plate) to form PTVnew. A rough PTV (PTVrough) was formed by giving a margin of 15 mm forward-downward (skull base) and 3 mm in the other directions. CRTold and IMRTold plans were designed based on PTVold. CRTnew and IMRTnew plans were designed based on PTVnew. CRTrough plan was designed based on PTVrough. The omission of sub-structures based on CTVold and the underdose of CTVsub in each plan were evaluated. Results A total of 78.6% of superior orbital fissure,71.99% of foramen rotundum,96.76% of foramen ovale,88.5% of jugular foramen,97.71% of hypoglossal canal,99.48% of internal auditory meatus and 100% of optic nerve volume were missed based on CTVold. The target dose coverage of CTVsub based on CRTold and IMRTold was only 91.70% and 89.83%, respectively. The underdose was observed in 16.66%,3.57%,20.83%,1.78% and 1.19% of sub-structures in CRTold,CRTnew,IMRTold,IMRTnew and CRTrough plans, respectively. Of the underdose of all sub-structures,38.36% and 46.58% occurred in CRTold and IMRTold plans, respectively. Among them,the least and the most significant underdose occurred in foramen rotundum (0%) and foramen ovale (36.66%),respectively. Conclusions As per the SIOPE guidelines, traditional brain tissue delineation (including sieve plate) is likely to omit part of the target during the cranial target definition of craniospinal irradiation. The most significant underdose occurs in foramen ovale,and more obvious in the IMRT plan. The plan based on the delineation of sub-structures can significantly improve the underdose. When AP-PA irradiation is adopted,a rough PTV is recommended to obtain approximate target dose coverage and organ of risk sparing,whereas it requires further clinical verification.