Reduced volume intensity-modulated radiotherapy with simultaneous integrated boost for patients with high-grade glioma: A retrospective observational study

Radiotherapy (RT) is an essential treatment for patients with high-grade gliomas. however, a consensus on the target area of RT has not yet been achieved. In this study, we aimed to analyze progression-free survival (PFS), recurrence patterns, and toxicity in patients who received reduced volume intensity-modulated radiotherapy with simultaneous integrated boost (rvSIB-IMRT). In addition, we attempted to identify prognostic factors for recurrence. Twenty patients with high-grade gliomas who received rvSIB-IMRT between July 2011 and December 2021 were retrospectively analyzed. For rvSIB-IMRT, clinical target volume 1/2 was set at a 5 to 10 mm margin on each gross tumor volume (GTV) 1 (resection cavity and enhanced lesion) and GTV2 (high-signal lesion of T2/fluid-attenuated inversion recovery). RT doses were prescribed to 60 Gy/30 fractions (fxs) for planning target volume (PTV)1 and 51 to 54 Gy/30 fxs for PTV2. The median PFS and overall survival of the total cohorts were 10.6 and 13.6 months, respectively. Among the 12 relapsed patients, central, in-field, and marginal recurrences were identified in 8 (66.7%), 2 (16.7%), and 1 patient (8.3%), respectively. Distant recurrence was identified in 3 patients. Gross total resection (GTR) and high Ki-67 index (>27.4%), and subventricular involvement (SVI) were identified as significant factors for PFS in the multivariate analysis. During the follow up, 4 patients showed pseudoprogression and 1 patient showed radiation necrosis. The rvSIB-IMRT for high-grade gliomas resulted in comparable PFS and tolerable toxicity. Most recurrences were central/in-field (10 cases of 12, 83.4%). GTR, high Ki-67 index (>27.4%), and SVI were significant factors for recurrence.