Intraoperative radiotherapy for glioblastoma: A systematic review of techniques and outcomes

Background: Despite multimodality treatment, the prognosis of glioblastoma (GBM) has remained poor. Intraoperative radiation therapy (IORT) offers additional local control by directly applying a radiation source to the resection margin, where most recurrences occur. Methods: We performed a systematic review on the oncologic outcomes and toxicities of IORT for GBM in the era of modern external beam radiation therapy (EBRT) and chemotherapy with temozolamide. Results: Four studies representing 123 patients were included. Majority (81%) were newly diagnosed, and gross total resection was reported in 13-80% of cases. IORT modalities included electrons from a linear accelerator (LINAC) and photons from a 50-kV x-ray device. Median doses were from 12.5 to 20 Gy for electron-based studies and 10-25 Gy for photon-based studies. Adjuvant treatment consisted of 46- 60 Gy post-operative EBRT in electron-based studies and the Stupp protocol in photon-based studies. Complications included radiation necrosis (2.8-33%), infection, hematoma, perilesional edema, and wound dehiscence. Median time to local recurrence was 9.9-16 months and the reported overall progression-free survival was 11.2-12.2 months. Median overall survival was 13-14.2 months for the electron-based studies and 13.8-18 months for the photon-based studies. Conclusion: IORT resulted in improved local control and comparable overall survival rates with the Stupp protocol. Although photon-based IORT had better results than electron IORT, this may be due to improve-ments in other forms of adjuvant treatment rather than the IORT modality itself. The overall effect of IORT on GBM treatment is still inconclusive due to the small number of patients and heterogeneous reporting of data. (c) 2021 Elsevier Ltd. All rights reserved.