2Department of Radiation Oncology, Acıbadem Altunizade Hospital, İstanbul-Türkiye DOI : 10.5505/tjo.2022.3841 OBJECTIVE
This study aimed to investigate the boost volume changes on adaptive magnetic resonance imaging (MRI) performed before the second phase of the radiotherapy (RT) for glioblastoma (GBM) and to examine whether the extent of surgery affected the boost volume changes.
METHODS
Among 50 GBM patients included in this study, 30 had Gross total resection (GTR), 14 had STR (subtotal
resection), and sixpatients had biopsy.Treatments were planned in twophases according to the RTOG
recommendations. Computed tomography (CT) for treatment planning and MRI for target volume determination
were performed twice, before treatment and around the 20th fraction. Boost volumes were
delineated on both images to compare volume changes.Wilcoxon two-related t-test was used to evaluate
the boost volume changes. Growth and shrinkage trends were analyzed according to the type of resection.
RESULTS
The change between the determined boost volumes on two scans wasfound to be statistically significant.
Twenty-four of 30 patients (80%) who underwent GTR had a reduced GTV, and threehad enlargement.
Among patients who had an STR, GTV volume decreased in sevenof 14 patients (50%) and enlarged in
6 (43%).GTV shrank in twoof sixpatients (33%) with biopsy and enlarged in four.
CONCLUSION
This study demonstrated that there were considerable radiological changes occurring during RT for
GBM patients. The boost volume variations occurring during RT require repeat CT/MRI for the second
phase of RT. The extent of surgery can be considered while generating CTV and PTV margins.