Radiation Therapy for Grade 3 Gliomas: Correlation of MRI Findings With Prognosis

Abstract

Background and objectivePostoperative radiotherapy is usually indicated for both grade 3 glioma and grade 4 glioblastoma. However, the treatment results and tumor features of grade 3 glioma clearly differ from those of glioblastoma. There is limited information on outcomes and tumor progression for grade 3 glioma. In this study, we evaluate the result of postoperative radiotherapy for grade 3 glioma and focus on the correlation of MRI findings with prognosis. MethodsIn this study, 99 of 110 patients with grade 3 glioma who received postoperative radiotherapy and were followed up for more than one year were retrospectively analyzed. The total irradiation dose was 60.0 Gy in 30 fractions, and daily temozolomide or two cycles of nimustine (ACNU) was concurrently administered during radiotherapy. The median follow-up period was 46 months (range: 2-151 months). ResultsIn multivariate analysis, pathology [anaplastic oligodendroglioma (AO) vs. anaplastic astrocytoma (AA)], the status of surgical resection (biopsy vs. partial resection or more), and contrast enhancement (enhanced by MRI image or not) were significant factors for overall survival (OS). The five-year OS for AO vs. AA cases were 76.8% vs. 46.1%, total to partial resection vs. biopsy cases were 72.7% vs. 21.0%, and non-enhanced vs. enhanced cases were 82.5% vs. 45.6%, respectively. In multivariate analysis, the status of surgical resection and longer extension of preoperative edema (PE) were significant factors for progression-free survival (PFS). The five-year PFS for the total to partial resection vs. biopsy cases were 52.9% vs. 10.7%, and non-extensive PE vs. extensive PE (EPE) cases were 62.2% vs. 19.1%, respectively. ConclusionOur results suggest that a contrast-enhanced tumor on MRI and a longer PE may also be significantly associated with OS and PFS among grade 3 glioma patients.

Factors Involved in Preoperative Edema in High-Grade Gliomas

“…The results of this study based on quantitative evaluation of edema are consistent with this finding. Liang et al found that the E/T ratio contributes significantly to OS [ 7 ], and other reports have shown that PE (without consideration of tumor volume) is a prognostic factor in G3 or G4 glioma [ 3 , 6 ]. Therefore, the E/T ratio and PE are both useful prognostic factors for gliomas that can be objectively assessed on conventional MRI.…”

“…Such edema promotes tumor cell infiltration into the surrounding area, which extends the range over which the tumor can expand [2]. In Grade 3 (G3) and Grade 4 (G4) gliomas, extensive preoperative edema (PE) can be readily identified on magnetic resonance imaging (MRI) and has been found to be a poor prognostic factor [3][4][5][6]. The degree of edema can be classified into categories, but may also be described numerically [6,7].…”

“…In Grade 3 (G3) and Grade 4 (G4) gliomas, extensive preoperative edema (PE) can be readily identified on magnetic resonance imaging (MRI) and has been found to be a poor prognostic factor [3][4][5][6]. The degree of edema can be classified into categories, but may also be described numerically [6,7]. This numerical approach permits the use of PE as an indicator that can be easily measured and is not limited by subjective differences among raters.…”