The influence of peritumoral edema on the efficacy of radiation therapy in glioblastoma treatment: a retrospective study

Background Radiation therapy is a crucial treatment method for glioblastoma (GBM). However, the definition of clinical target volume (CTV) varies across different institution and remains a topic of debate. In this study, we reviewed and analyzed the impact of a novel target delineation radiotherapy regimen on the survival, prognosis, and recurrence patterns of GBM. Our findings provide evidence to support the optimal target delineation for GBM. Methods We collected clinical data from 50 patients with GBM (including progression-free survival (PFS) and overall survival (OS)) whose target area was defined as tumor volume expansion of 10mm, extending into the edema area. We then generated simulated EORTC targets to assess recurrence patterns in both targets. The Kaplan-Meier method was utilized to estimate survival time, the chi-square test was used to compare the cohorts. Results The PFS was 11.87 months (95% CI: 10.29–13.44), and the OS was 17.47 months (95% CI: 11.58–23.36). The new target delineation radiotherapy protocol did not alter the recurrence pattern of GBM patients, 46 (92%) patients experienced recurrence within the target area, while 4 (8%) recurred outside the target area. The recurrence site was an average of 6.23mm from the primary site (range, 0.00–22.17mm), and the median CTV volume was 130.56mm³ (range, 38.89–269.27mm ³ ). Conclusions The updated radiotherapy protocol for GBM did not change the recurrence pattern but could improve the prognosis. This discovery may establish a novel foundation for the involvement of edematous regions in defining target volumes in GBM.