Explore The Reasonable Postoperative Target Area Of Glioblastoma Based On The Recurrence Pattern

Objective:Although radiotherapy（RT）is a fundamental component of the systemic therapy for Glioblastoma multiforme（GBM）,the optimal treatment volume is still a controversial issue worldwide.The purpose of this study is to analyze the distance between the recurring tumors and the edge of the primary lesions,and thereby provide evidence for accurate target area delineation.Methods:Between October 2007 and March 2019 in Jiangxi Provincial Cancer Hospital,all patients with recurrent glioblastoma confirmed by radiology and exclude patients without postperative imaging and radiotherapy plans,68 recurrent patients with GBM were included in our study.In this study,Pinnacle treatment planning system image fusion was used to integrate radiotherapy localization MRI and MRI at the first relapse into the radiotherapy plan,and outline the MR images of the primary lesion enhancement area GTV_T1+C,Flair area GTV_Flair,relapse enhancement focus rGTV_T1+C,Determine the three-dimensional center of the recurring focus through the treatment planning system,and measure the shortest distances D_T11 and D_T22 between the center of the recurring focus and the edges of GTV_T1+C1+C and GTV_Flairlair in three-dimensional space.Calculate the volume percentage of rGTV_T1+C1+C in the 95%isodose line of the prescribed dose.If it is greater than 80%,20%-80%or less than20%,then the recurrent tumor is defined as relapse in the field,marginal or distant.Results:Recurrences were local in 56（82.3%）patients,including 45 patients of simple field recurrence and 2 patients of simple marginal recurrence;distant in 21（30.9%）patients,including 12 patients of simple distant dissemination;among them,9（13.2%）patients were both local and distant recurrence simultaneously.Factors significantly influencing local recurrence were age（P=0.049）,sex（P=0.049）,and the size of peritumoral edema（P=0.00）.A total number of 91 recurrent tumors were analyzed with 58 local and 33 distant lesions.All local recurrences occurred within 2.0cm and94.8%occurred within 1.0cm of the original GTV_T1+C.All local recurrences occurred within 1.5cm and 98.3%occurred within 0.5cm of the original GTV_Flair.The center of33 distant recurrent lesions at GTV_T1+C1+C and GTV_Flairlair margins greater than 3.0cm were90.9%（30/33）and 81.8%（27/33）,respectively.Conclusions:Local recurrence is the main recurrence pattern after GBM postoperative chemotherapy,The 1cm margin from GTV_T1+C1+C and 0.5cm margin from GTV_Flairlair could cover 94.8%and 98.3%local recurrences respectively,which deserves further prospective study as a limited but effective target area.Most distant resuscitation stakes outside 3.0 cm of the original lesions,exceeding the current range of treatment in most cancer centres.