**2.3. High grade glioma surgical options**

Recommended treatment for grade III and IV glioma, glioblastoma multiforme (GBM), includes maximally safe resection, if feasible, administration of temozolomide with combination of radiotherapy and chemotherapy depending of favorable and unfavorable prognostic factors and glioma features [20]. The median OS for GMB is 15 months and for grade III tumors between 3.5 and 10 years [14, 25]. In surgical treatment, STR shows better OS compared to biopsy without increasing morbidity [8]. As shown in a meta-analysis of 12,607 high-graded glioma in elderly patients, biopsy OS *vs*. STR was 5.71 months *vs.* 8.68 months, respectively, with lower morbidity rate and longer progression free survival in STR patients [21]. In studies assessing the extent of resection (EOR) in high-grade glioma, in the so-called volumetric studies, STR showed a shorter OS of 2 to 8 months; in nonvolumetric studies, OS was also shorter by 0.9 to 8 months [7]. In their study, Chaichana et al. showed that residual volume and EOR are independent values for OS and GBM recurrence. They found that the residual volume of <2 cm3 with 95% resection has the greatest reduction in death in GBM patients [14]. Because of this EOR feature, it is mandatory to perform GTR always when possible, depending on tumor location and quality of life after GTR. GTR has superiority over STR in elderly patients with high grade glioma. GTR resulted in better OS, PFS, and Karnofsky performance score [21]. In children with mean age of 11 years, GTR of high grade glioma resulted in better OS than STR, 3.4 years *vs.* 1.6 years, respectively. Female patients with GTR also had a better OS than male patients, 8.1 years *vs.* 2.4 years, respectively [26]. Concerning higher grade glioma, supratotal resection can have some benefits. In a study of Li et al. of 876 patients who had a GTR (100% EOR), 643 underwent resection of T2 FLAIR abnormality region. Approximately, 18% of them had negative EOR due to postoperative edema, and in positive patients—more than 53.21%— FLAIR resection was associated with improved OS compared with patients with less than 53.21% FLAIR resection (20.7 months *vs.* 15.5 months, p < 0.001) [27]. With supratotal resection, the usage of chemotherapy and radiotherapy was reduced after supratotal resection.
