Distinct IDH1/IDH2 mutation profiles in purely insular versus paralimbic WHO Grade II gliomas

Survival outcome and predictors of WHO grade 2 and 3 insular gliomas: A classification based on the tumor spread

OBJECTIVE

The study aimed to identify if clinical features and survival outcomes of insular glioma patients are associated with our classification based on the tumor spread.

METHODS

Our study included 283 consecutive patients diagnosed with histological grade 2 and 3 insular gliomas. A new classification was proposed, and tumors restricted to the paralimbic system were defined as type 1. When tumors invaded the limbic system (referred to as the hippocampus and its surrounding structures in this study) simultaneously, they were defined as type 2. Tumors with additional internal capsule involvement were defined as type 3.

RESULTS

Tumors defined as type 3 had a higher age at diagnosis (p = 0.002) and a higher preoperative volume (p < 0.001). Furthermore, type 3 was more likely to be diagnosed as IDH wild type (p < 0.001), with a higher rate of Ki-67 index (p = 0.015) and a lower rate of gross total resection (p < 0.001). Type 1 had a slower tumor growth rate than type 2 (mean 3.3%/month vs. 19.8%/month; p < 0.001). Multivariate Cox regression analysis revealed the extent of resection (HR 0.259, p = 0.004), IDH status (HR 3.694, p = 0.012), and tumor spread type (HR = 1.874, p = 0.012) as independent predictors of overall survival (OS). Tumor grade (HR 2.609, p = 0.008), the extent of resection (HR 0.488, p = 0.038), IDH status (HR 2.225, p = 0.025), and tumor spread type (HR 1.531, p = 0.038) were significant in predicting progression-free survival (PFS).

CONCLUSION

The current study proposes a classification of the insular glioma according to the tumor spread. It indicates that the tumors defined as type 1 have a relatively better nature and biological characteristics, and those defined as type 3 can be more aggressive and refractory. Besides its predictive value for prognosis, the classification has potential value in formulating surgical strategies for patients with insular gliomas.

Prognostic Factors and Resectability Predictors in Insular Gliomas: A Systematic Review

BACKGROUND

 Insular gliomas (INGs) remain a surgically intimidating glioma subgroup encased by eloquent cortical parcels and white matter language tracts, and traversed by multiple middle cerebral artery branches. The predictive power of prognostic factors affecting overall survival (OS), progression-free survival (PFS), and resectability of INGs remain disputed. This comprehensive systematic review analyses prognostic factors and resectability predictors of INGs substantiating pragmatic management options.

MATERIALS AND METHODS

 A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) and the Cochrane Handbook of Systematic Reviews of Interventions guidelines. The PubMed, MEDLINE, and Embase databases were searched in April 2022. All clinical studies with ≥10 patients harboring INGs with any intervention and reporting predictors of OS, PFS, and tumor resectability in INGs were included. Molecular ING prognosticators were also included. Studies combining insular and other gliomas analysis, case studies, experimental and animal studies, conference abstracts, letters to the editor, and articles in other languages were excluded.

RESULTS

 Of the 2,384 articles returned, 27 fulfilled the inclusion criteria totaling 1,985 patients. The review yielded 18 OS and 17 PFS prognosticators. These were classified as preoperative (radiologic; clinical), intraoperative, and postoperative (molecular; histopathologic; clinical) prognosticators. In addition, 21 resectability predictors were categorized as preoperative (radiologic; clinical), intraoperative (surgical approach and assistive technology), and postoperative (histopathologic; clinical). The quality assessment revealed 24/27 studies had low risk of bias. One study with moderate and two studies with high risk of bias were included.

CONCLUSION

 Negative prognosticators reported in ≥2 studies included putaminal or paralimbic involvement and higher tumor grade, while seizures at presentation, isocitrate dehydrogenase (IDH) mutation, increased extent of resection, and higher Karnofsky Performance Status preoperatively and at 3 months postoperation were positive prognosticators. Resectability predictors reported in ≥2 studies included the positive predictors of zone I/zone IV tumor location and intraoperative imaging use and the negative predictor of encased lenticulostriate arteries. Paralimbic INGs are not a single entity with homogeneous prognosis. Integration of identified prognosticators in a prospective trial to devise a grading system for INGs can improve clinical decision-making.

A Review on the Surgical Management of Insular Gliomas

The surgical treatment of insular gliomas requires specialized knowledge. Over the last three decades, increased momentum in surgical resection of insular gliomas shifted the focus from one of expectant management to maximal safe resection to establish a diagnosis, characterize tumor genetics, treat preoperative symptoms (i.e., seizures), and delay malignant transformation through tumor cytoreduction. A comprehensive review of the literature was performed regarding insular glioma classification/genetics, insular anatomy, surgical approaches, and patient outcomes. Modern large, published series of insular resections have reported a median 80% resection, 80% improvement in preoperative seizures, and postsurgical permanent neurologic deficits of less than 10%. Major complication avoidance includes recognition and preservation of eloquent cortex for language and respecting the lateral lenticulostriate arteries.

Preoperative imaging features: Are they useful tools for predicting IDH1 mutation status in gliomas Grades II–IV?

Background:

It is already known that gliomas biomolecular parameters have a reliable prognostic value. However, an invasive procedure is required to determine them. Our aim was to better understand the clinical characteristics of gliomas Grades II–IV and to assess the usefulness of imaging features in magnetic resonance imaging (MRI) to predict the isocitrate dehydrogenase one (IDH1) mutation.

Methods:

Preoperative MRI characteristics were retrospectively reviewed and molecular diagnosis of gliomas was tested in adult patients between 2014 and 2021 in two institutions. We applied a biological criterion to divide the brain in cerebral compartments.

Results:

A total of 108 patients met the inclusion criteria. Contrast enhancement (CE) in MRI was significantly associated with wild-type IDH1 (IDH1-Wt) (P < 0.00002). Furthermore, the positive predictive value of CE for IDH1-Wt was of 87.1%. On the other hand, the negative predictive value of non-CE for mutated IDH1 (IDH1-Mut) was of 52.6%; 60.2% of gliomas were located in the neocortical and 24.1% in the allocortical/mesocortical telencephalon. Considering gliomas Grades II–III, 66.7% of IDH1-Mut and 28.6% of IDH1-Wt gliomas were located in the neocortex, without statistical significance.

Conclusion:

Our research revealed that CE is useful for predicting IDH1-Wt in gliomas. On the contrary, nonCE is not useful for predicting IDH1-Mut gliomas. Thus, the traditional concept of associating non-CE MRI with a low-grade glioma should be reviewed, as it can lead to an underestimation of the potential aggressiveness of the tumor. If this association was validated with the future prospective studies, a noninvasive tool would be available for predicting gliomas IDH1 mutation status.

Preoperative and Noninvasive Prediction of Gliomas Histopathological Grades and IDH Molecular Types Using Multiple MRI Characteristics

Background and Purpose

Gliomas are one of the most common tumors in the central nervous system. This study aimed to explore the correlation between MRI morphological characteristics, apparent diffusion coefficient (ADC) parameters and pathological grades, as well as IDH gene phenotypes of gliomas.

Methods

Preoperative MRI data from 166 glioma patients with pathological confirmation were retrospectively analyzed to compare the differences of MRI characteristics and ADC parameters between the low-grade and high-grade gliomas (LGGs vs. HGGs), IDH mutant and wild-type gliomas (IDH^mut vs. IDH^wt). Multivariate models were constructed to predict the pathological grades and IDH gene phenotypes of gliomas and the performance was assessed by the receiver operating characteristic (ROC) analysis.

Results

Two multivariable logistic regression models were developed by incorporating age, ADC parameters, and MRI morphological characteristics to predict pathological grades, and IDH gene phenotypes of gliomas, respectively. The Noninvasive Grading Model classified tumor grades with areas under the ROC curve (AUROC) of 0.934 (95% CI=0.895-0.973), sensitivity of 91.2%, and specificity of 78.6%. The Noninvasive IDH Genotyping Model differentiated IDH types with an AUROC of 0.857 (95% CI=0.787-0.926), sensitivity of 88.2%, and specificity of 63.8%.

Conclusion

MRI features were correlated with glioma grades and IDH mutation status. Multivariable logistic regression models combined with MRI morphological characteristics and ADC parameters may provide a noninvasive and preoperative approach to predict glioma grades and IDH mutation status.

Correlation of anatomical involvement patterns of insular gliomas with subnetworks of the limbic system

OBJECTIVE

Gliomas frequently involve the insula both primarily and secondarily by invasion. Despite the high connectivity of the human insula, gliomas do not spread randomly to or from the insula but follow stereotypical anatomical involvement patterns. In the majority of cases, these patterns correspond to the intrinsic connectivity of the limbic system, except for tumors with aggressive biology. On the basis of these observations, the authors hypothesized that these different involvement patterns may be correlated with distinct outcomes and analyzed these correlations in an institutional cohort.

METHODS

Fifty-nine patients who had undergone surgery for insular diffuse gliomas and had complete demographic, pre- and postoperative imaging, pathology, molecular genetics, and clinical follow-up data were included in the analysis (median age 37 years, range 21-71 years, M/F ratio 1.68). Patients with gliomatosis and those with only minor involvement of the insula were excluded. The presence of T2-hyperintense tumor infiltration was evaluated in 12 anatomical structures. Hierarchical biclustering was used to identify co-involved structures, and the findings were correlated with established functional anatomy knowledge. Overall survival was evaluated using Kaplan-Meier and Cox proportional hazards regression analysis (17 parameters).

RESULTS

The tumors involved the anterior insula (98.3%), posterior insula (67.8%), temporal operculum (47.5%), amygdala (42.4%), frontal operculum (40.7%), temporal pole (39%), parolfactory area (35.6%), hypothalamus (23.7%), hippocampus (16.9%), thalamus (6.8%), striatum (5.1%), and cingulate gyrus (3.4%). A mean 4.2 ± 2.6 structures were involved. On the basis of hierarchical biclustering, 7 involvement patterns were identified and correlated with cortical functional anatomy (pure insular [11.9%], olfactocentric [15.3%], olfactoopercular [33.9%], operculoinsular [15.3%], striatoinsular [3.4%], translimbic [11.9%], and multifocal [8.5%] patterns). Cox regression identified hippocampal involvement (p = 0.006) and postoperative tumor volume (p = 0.027) as significant negative independent prognosticators of overall survival and extent of resection (p = 0.015) as a significant positive independent prognosticator.

CONCLUSIONS

The study findings indicate that insular gliomas primarily involve the olfactocentric limbic girdle and that involvement in the hippocampocentric limbic girdle is associated with a worse prognosis.

Cortical and Subcortical Anatomy of the Orbitofrontal Cortex: A White Matter Microfiberdissection Study and Case Series

BACKGROUND

The literature on white matter anatomy underlying the human orbitofrontal cortex (OFC) is scarce in spite of its relevance for glioma surgery.

OBJECTIVE

To describe the anatomy of the OFC and of the underlying white matter fiber anatomy, with a particular focus on the surgical structures relevant for a safe and efficient orbitofrontal glioma resection. Based on anatomical and radiological data, the secondary objective was to describe the growth pattern of OFC gliomas.

METHODS

The study was performed on 10 brain specimens prepared according to Klingler's protocol and dissected using the fiber microdissection technique modified according to U.T., under the microscope at high magnification.

RESULTS

A detailed stratigraphy of the OFC was performed, from the cortex up to the frontal horn of the lateral ventricle. The interposed neural structures are described together with relevant neighboring topographic areas and nuclei. Combining anatomical and radiological data, it appears that the anatomical boundaries delimiting and guiding the macroscopical growth of OFC gliomas are as follows: the corpus callosum superiorly, the external capsule laterally, the basal forebrain and lentiform nucleus posteriorly, and the gyrus rectus medially. Thus, OFC gliomas seem to grow ventriculopetally, avoiding the laterally located neocortex.

CONCLUSION

The findings in our study supplement available anatomical knowledge of the OFC, providing reliable landmarks for a precise topographical diagnosis of OFC lesions and for perioperative orientation. The relationships between deep anatomic structures and glioma formations described in this study are relevant for surgery in this highly interconnected area.

World Health Organization Grade II/III Glioma Molecular Status: Prediction by MRI Morphologic Features and Apparent Diffusion Coefficient

Background A readily implemented MRI biomarker for glioma genotyping is currently lacking. Purpose To evaluate clinically available MRI parameters for predicting isocitrate dehydrogenase (IDH) status in patients with glioma. Materials and Methods In this retrospective study of patients studied from July 2008 to February 2019, untreated World Health Organization (WHO) grade II/III gliomas were analyzed by three neuroradiologists blinded to tissue results. Apparent diffusion coefficient (ADC) minimum (ADC_min) and mean (ADC_mean) regions of interest were defined in tumor and normal appearing white matter (ADC_NAWM). A visual rating of anatomic features (T1 weighted, T1 weighted with contrast enhancement, T2 weighted, and fluid-attenuated inversion recovery) was performed. Interobserver comparison (intraclass correlation coefficient and Cohen κ) was followed by nonparametric (Kruskal-Wallis analysis of variance) testing of associations between ADC metrics and glioma genotypes, including Bonferroni correction for multiple testing. Descriptors with sufficient concordance (intraclass correlation coefficient, >0.8; κ > 0.6) underwent univariable analysis. Predictive variables (P < .05) were entered into a multivariable logistic regression and tested in an additional test sample of patients with glioma. Results The study included 290 patients (median age, 40 years; interquartile range, 33-52 years; 169 male patients) with 82 IDH wild-type, 107 IDH mutant/1p19q intact, and 101 IDH mutant/1p19q codeleted gliomas. Two predictive models incorporating ADC_mean-to-ADC_NAWM ratio, age, and morphologic characteristics, with model A mandating calcification result and model B recording cyst formation, classified tumor type with areas under the receiver operating characteristic curve of 0.94 (95% confidence interval [CI]: 0.91, 0.97) and 0.96 (95% CI: 0.93, 0.98), respectively. In the test sample of 49 gliomas (nine IDH wild type, 21 IDH mutant/1p19q intact, and 19 IDH mutant/1p19q codeleted), the classification accuracy was 40 of 49 gliomas (82%; 95% CI: 71%, 92%) for model A and 42 of 49 gliomas (86%; 95% CI: 76%, 96%) for model B. Conclusion Two algorithms that incorporated apparent diffusion coefficient values, age, and tumor morphologic characteristics predicted isocitrate dehydrogenase status in World Health Organization grade II/III gliomas on the basis of standard clinical MRI sequences alone. © RSNA, 2020 Online supplemental material is available for this article.

Huge heterogeneity in survival in a subset of adult patients with resected, wild-type isocitrate dehydrogenase status, WHO grade II astrocytomas

OBJECTIVE

World Health Organization grade II gliomas are infiltrating tumors that inexorably progress to a higher grade of malignancy. However, the time to malignant transformation is quite unpredictable at the individual patient level. A wild-type isocitrate dehydrogenase (IDH-wt) molecular profile has been reported as a poor prognostic factor, with more rapid progression and a shorter survival compared with IDH-mutant tumors. Here, the oncological outcomes of a series of adult patients with IDH-wt, diffuse, WHO grade II astrocytomas (AII) who underwent resection without early adjuvant therapy were investigated.

METHODS

A retrospective review of patients extracted from a prospective database who underwent resection between 2007 and 2013 for histopathologically confirmed, IDH-wt, non-1p19q codeleted AII was performed. All patients had a minimum follow-up period of 2 years. Information regarding clinical, radiographic, and surgical results and survival were collected and analyzed.

RESULTS

Thirty-one consecutive patients (18 men and 13 women, median age 39.6 years) were included in this study. The preoperative median tumor volume was 54 cm3 (range 3.5-180 cm3). The median growth rate, measured as the velocity of diametric expansion, was 2.45 mm/year. The median residual volume after surgery was 4.2 cm3 (range 0-30 cm3) with a median volumetric extent of resection of 93.97% (8 patients had a total or supratotal resection). No patient experienced permanent neurological deficits after surgery, and all patients resumed a normal life. No immediate postoperative chemotherapy or radiation therapy was given. The median clinical follow-up duration from diagnosis was 74 months (range 27-157 months). In this follow-up period, 18 patients received delayed chemotherapy and/or radiotherapy for tumor progression. Five patients (16%) died at a median time from radiological diagnosis of 3.5 years (range 2.6-4.5 years). Survival from diagnosis was 77.27% at 5 years. None of the 21 patients with a long-term follow-up greater than 5 years have died. There were no significant differences between the clinical, radiological, or molecular characteristics of the survivors relative to the patients who died.

CONCLUSIONS

Huge heterogeneity in the survival data for a subset of 31 patients with resected IDH-wt AII tumors was observed. These findings suggest that IDH mutation status alone is not sufficient to predict risk of malignant transformation and survival at the individual level. Therefore, the therapeutic management of AII tumors, in particular the decision to administer early adjuvant chemotherapy and/or radiation therapy following surgery, should not solely rely on routine molecular markers.

Clinical considerations and surgical approaches for low-grade gliomas in deep hemispheric locations: insular lesions

Insula and paralimbic region represent a common location for gliomas in adulthood. However, limbic and paralimbic tumors are rare in children. Reports of pediatric insular tumors are scarce in literature, and most of them are included in adult's series, so their management and outcome can be outlined only after extracting data from these reports. Due to their predominantly low grade, they usually have a benign course for some time, what make them ideal candidates for total resection. However, their intricate location and spread to key areas, including the temporal lobe, make them a surgical challenge. The transsylvian route, with or without resection of the frontal and/or temporal operculae, which requires exposure of part or all of the insula is commonly selected for insular tumor approaches. Intraoperative functional mapping is a standard procedure for resection of central region tumors in adults. In children and young individuals, awake craniotomy is not always possible and surgical planning usually relay on functional and anatomical preoperative studies. The main goal when approaching an insular tumor is to achieve the largest extent of resection to increase overall patient survival while preserving the functional status, minimizing postoperative morbidity and increasing the quality of life. The extent of resection seems to be correlated also with the control of associated (and usually intractable) epilepsy.

Putamen involvement and survival outcomes in patients with insular low-grade gliomas

OBJECTIVE Insular glioma has a unique origin and biological behavior; however, the associations between its anatomical features and prognosis have not been well established. The object of this study was to propose a classification system of insular low-grade gliomas based on preoperative MRI findings and to assess the system's association with survival outcome. METHODS A total of 211 consecutively collected patients diagnosed with low-grade insular gliomas was analyzed. All patients were classified according to whether tumor involved the putamen on MR images. The prognostic role of this novel putaminal classification, as well as that of Yaşargil's classification, was examined using multivariate analyses. RESULTS Ninety-nine cases (46.9%) of insular gliomas involved the putamen. Those tumors involving the putamen, as compared with nonputaminal tumors, were larger (p < 0.001), less likely to be associated with a history of seizures (p = 0.04), more likely to have wild-type IDH1 (p = 0.003), and less likely to be totally removed (p = 0.02). Significant favorable predictors of overall survival on univariate analysis included a high preoperative Karnofsky Performance Scale score (p = 0.02), a history of seizures (p = 0.04), gross-total resection (p = 0.006), nonputaminal tumors (p < 0.001), and an IDH1 mutation (p < 0.001). On multivariate analysis, extent of resection (p = 0.035), putamen classification (p = 0.014), and IDH1 mutation (p = 0.026) were independent predictors of overall survival. No prognostic role was found for Yaşargil's classification. CONCLUSIONS The current study's findings suggest that the putamen classification is an independent predictor of survival outcome in patients with insular low-grade gliomas. This newly proposed classification allows preoperative survival prediction for patients with insular gliomas.

Second Surgery in Insular Low-Grade Gliomas

Background. Given the technical difficulties, a limited number of works have been published on insular gliomas surgery and risk factors for tumor recurrence (TR) are poorly documented. Objective. The aim of the study was to determine TR in adult patients with initial diagnosis of insular Low-Grade Gliomas (LGGs) that subsequently underwent second surgery. Methods. A consecutive series of 53 patients with insular LGGs was retrospectively reviewed; 23 patients had two operations for TR. Results. At the time of second surgery, almost half of the patients had experienced progression into high-grade gliomas (HGGs). Univariate analysis showed that TR is influenced by the following: extent of resection (EOR) (P < 0.002), ΔVT2T1 value (P < 0.001), histological diagnosis of oligodendroglioma (P = 0.017), and mutation of IDH1 (P = 0.022). The multivariate analysis showed that EOR at first surgery was the independent predictor for TR (P < 0.001). Conclusions. In patients with insular LGG the EOR at first surgery represents the major predictive factor for TR. At time of TR, more than 50% of cases had progressed in HGG, raising the question of the oncological management after the first surgery.

Mediobasal and lateral temporal gliomas exhibit different growth patterns, surgical outcomes and prognoses

OBJECTIVE

This study was aimed at investigating the differences between mediobasal temporal gliomas and lateral temporal gliomas.

METHODS

One hundred and forty-seven patients with temporal gliomas who were admitted in the Department of Supratentorial Neoplasms at Beijing Tiantan Hospital between 2008 and 2011 were included in this prospective study. Temporal gliomas involving the limbic and paralimbic systems were classified as mediobasal temporal gliomas (MTGs), while those without the involvement of the limbic and paralimbic systems were defined as lateral temporal gliomas (LTGs). The clinical, radiological, histopathological, and molecular features were compared between MTG and LTG patients.

RESULTS

Compared to LTGs, MTGs were significantly larger in size (P = 0.013) and displayed a more aggressive invasion of surrounding tissues (P < 0.001). Marginally significant differences of the IDH1/2 mutation rate were observed between MTG and LTG patients (P = 0.058). The postoperative disability rate of MTGs was significantly higher than that of LTGs (P = 0.031). Resection degree according to tumor grade between LTG and MTG showed no statistical significance, while it mixed all grades showed marginally significant difference (P = 0.060). Regardless of tumor grade, the PFS and OS of MTG was shorter than that of LTG, except for OS in grade II (P = 0.189).

CONCLUSIONS

Temporal gliomas can be classified into two types, MTG and LTG which have different growth patterns, surgical outcomes and prognoses. Due to the significantly worse prognosis of patients with MTGs, this classification is useful for the clinical prognostic prediction of temporal gliomas.

ATRX mRNA expression combined with IDH1/2 mutational status and Ki-67 expression refines the molecular classification of astrocytic tumors: evidence from the whole transcriptome sequencing of 169 samples samples

Astrocytic tumors are the most common primary brain tumors in adults. ATRX mutations have been identified in gliomas and are correlated with its loss of expression, which causes alternative lengthening of telomeres (ALT) leading to genomic instability. In this study, we aimed to explore the role of ATRX mRNA expression alteration in the progression and subclassification of astrocytic tumors and examine its impact on clinical outcome. We investigated ATRX mRNA expression and its association with IDH1 and IDH2 mutations in 169 adult astrocytic tumors using whole transcriptome sequencing. In our cohort, low ATRX mRNA expression was detected in 68% of astrocytomas, 50% of anaplastic astrocytomas and 41.6% of glioblastomas. Low ATRX expression closely overlapped with mutations in IDH1/2 (P<0.0001) in astrocytic tumors across WHO grades II–IV. Significant association between low ATRX expression and longer overall survival was identified in our cohort (P<0.01). ATRX combined with IDH1/2 and Ki-67 was used to re-classify patients with astrocytic tumors: group A1 containing IDH1/2 mutations and low ATRX expression predicted a better prognostic outcome, whereas group A3 carrying wild-type IDH1/2 and high Ki-67 expression had the shortest overall survival; IDH-mutant tumors with low ATRX expression and IDH-wild-type tumors with high Ki-67 expression were grouped into group A2. In summary, our results showed that ATRX in cooperation with IDH1/2 and Ki-67 defines three subgroups of astrocytic tumors regardless of the conventional WHO grades consensus. The molecular stratification in astrocytic tumors may aid in treatment strategy selection, therapeutic trial design, and clinical prognosis evaluation.

A better surgical resectability of WHO grade II gliomas is independent of favorable molecular markers

A higher extent of resection (EOR) in WHO grade II gliomas (GIIG) is correlated with longer survival. However, the molecular markers also feature prognostic relevance. Here, we examined whether maximal EOR was related to the genetic profile. We retrospectively investigated the predictive value of 1p19q, IDH1, 53 expression and Ki67 index for the EOR in 200 consecutive GIIGs (2007-2013). Data were modeled in a linear model. The analysis was performed with two statistical methods (arcsin-sqrt and Beta-regression model with logit link). There was no deletion 1p19q in 118 cases, codeletion 1p19q (57 cases), single deletion 1p (4 cases) or19q (16 cases). 155 patients had a mutation of IDH1. p53 was graded in 4 degrees (0:92 cases, 1:52 cases, 2:31 cases, 3:8 cases). Mean Ki67 index was 5.2 % (range 1-20 %). Mean preoperative tumor volume was 60.8 cm(3) (range 3.3-250 cm(3)) and mean EOR was 0.917 (range 0.574-1). The statistical analysis was significant for a lower EOR in patients with codeletion 1p19q (OR 0.738, p = 0.0463) and with a single deletion 19q (OR 0.641, p = 0.0168). There was no significant correlation between IDH1 or p53 and the EOR. Higher Ki67 was marginally associated with higher EOR (p = 0.0603). The study demonstrates in a large cohort of GIIG that a higher EOR is not attributable to favorable genetic markers. This original result supports maximal surgical resection as an important therapeutic factor per se to optimize prognosis, independently of the molecular pattern.