Abstract
BackgroundPatients with glioblastoma multiforme (GBM) require radiotherapy as part of definitive management. Our institution has adopted the use of volumetric arc therapy (VMAT) due to superior sparing of the adjacent organs at risk (OARs) compared to intensity modulated radiation therapy (IMRT). Here we report our clinical experience by analyzing target coverage and sparing of OARs for 90 clinical treatment plans.MethodsVMAT and IMRT patient cohorts comprising 45 patients each were included in this study. For all patients, the planning target volume (PTV) received 50 Gy in 30 fractions, and the simultaneous integrated boost PTV received 60 Gy. The characteristics of the two patient cohorts were examined for similarity. The doses to target volumes and OARs, including brain, brainstem, hippocampi, optic nerves, eyes, and cochleae were then compared using statistical analysis. Target coverage and normal tissue sparing for six patients with both clinical IMRT and VMAT plans were analyzed.ResultsPTV coverage of at least 95% was achieved for all plans, and the median mean dose to the boost PTV differed by only 0.1 Gy between the IMRT and VMAT plans. Superior sparing of the brainstem was found with VMAT, with a median difference in mean dose being 9.4 Gy. The ipsilateral cochlear mean dose was lower by 19.7 Gy, and the contralateral cochlea was lower by 9.5 Gy. The total treatment time was reduced by 5 min. The difference in the ipsilateral hippocampal D100% was 12 Gy, though this is not statistically significant (P = 0.03).ConclusionsVMAT for GBM patients can provide similar target coverage, superior sparing of the brainstem and cochleae, and be delivered in a shorter period of time compared with IMRT. The shorter treatment time may improve clinical efficiency and the quality of the treatment experience. Based on institutional clinical experience, use of VMAT for the treatment of GBMs appears to offer no inferiority in comparison to IMRT and may offer distinct advantages, especially for patients who may require re-irradiation.
Highlights
Patients with glioblastoma multiforme (GBM) require radiotherapy as part of definitive management
For the two different patients cohorts (IMRT vs. volumetric arc therapy (VMAT)), there was no statistical difference in diagnosis, tumor location, tumor side, planning target volumes and brain volume between the
None of the investigated hippocampal doses were found to be statistically significant, and both the contralateral and bilateral D100% and Dmax were similar between the VMAT and intensity modulated radiation therapy (IMRT) cohorts. These results suggest a trend towards VMAT resulting in improved hippocampal sparing, which may offer a distinct advantage for certain patients
Summary
Patients with glioblastoma multiforme (GBM) require radiotherapy as part of definitive management. The definitive treatment of glioblastoma multiforme (GBM) typically includes maximal safe resection followed by chemotherapy and radiation therapy (RT) [1, 2]. These tumors have inherent radioresistance [3], tend to recur locally [4,5,6,7,8,9] and recent studies have shown the median time to progression to be 7–9 months [6,7,8,9]. Because life expectancy can be drastically reduced in patients with GBM, maintaining neurological function and the ability to perform daily activities can be an important treatment
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