Prognostic Analysis in Malignant Gliomas: Relationship between Brain Perfusion Magnetic Resonance and Methylation Analysis of MGMT Gene Promoter

Research Article

Austin Neurosurg Open Access. 2016; 3(2): 1053.

Prognostic Analysis in Malignant Gliomas: Relationship between Brain Perfusion Magnetic Resonance and Methylation Analysis of MGMT Gene Promoter

Gepp RA¹*, Rocque AL², Martins BJFA³, Batista GR4, Farage L4 and Pratesi R5

¹Neurosurgery Department, SARAH Network of Rehabilitation Hospitals, Brazil

²Molecular Genetics Laboratory, SARAH Network of Rehabilitation Hospitals, Brazil

³Radiology Department, SARAH Network of Rehabilitation Hospitals, Brazil

4Radiology Department, Medical School, University of Brasilia, Brazil

5University of Brasilia, Brazil

*Corresponding author: Ricardo A. Gepp, Neurosurgery Department, SARAH Network of Rehabilitation Hospitals,SQSW 300 Bloco D, apt 104 Brasília, DF, Brazil

Received: July 11, 2016; Accepted: October 11, 2016; Published: October 14, 2016


Objective: MRI is the current standard in the diagnostic of brain tumors, but images are insufficient for the prognostic assessment. MGMT promoter methylation is an important factor in the prognosis. The aim of the study was to examine the relationship between perfusion MRI and MGMT promoter methylation.

Methods: A total of 39 patients were evaluated. Statistical analysis and a study of the survival of the methylated and unmethylated groups were performed. Perfusion MRI for each group and the survival curves were constructed.

Results: Survival of patients negative for MGMT promoter methylation was 17.9 months, while in the methylation-positive was 29.2 (p<0.05). Survival of MGMT promoter methylation positive, in relation to perfusion, showed that variations between high and low perfusion values were not significant (p=0.944). Patients with no methylation and with high perfusion had poorer survival (p=0.038).

Conclusion: The presence of MGMT promoter methylation in conjunction with low perfusion are factors of better prognosis in gliomas.

Keywords: Glioma; Magnetic resonance imaging; Comparative study; Prognosis


Malignant gliomas are the most frequent primary tumor of the Central Nervous System (CNS) in adults. The cornerstone treatment in CNS tumors is the triad: surgery, chemotherapy and radiation therapy. Despite all technological progress, survival is still poor [1]. Magnetic resonance is the current standard imaging diagnostic tool, providing anatomical and functional images. Anatomical findings have been proven insufficient for the prognostic assessment of brain tumors; therefore, other methods with functional assessment are necessary [2]. Studies like Dynamic Susceptibility-Weighted Contrast-Enhanced (DSC) perfusion Magnetic Resonance Imaging (MRI) with the measurement of Relative Cerebral Blood Volume (rCBV) shows a good correlation with the presence of Vascular Endothelial Growth Factor (VEGF) [3,4].

The imaging-based criteria in assessing tumor recurrence has been changing with the introduction of new drugs such as Temozolomide and Bevacizumab: the MacDonald criteria (1990) are becoming less relevant, while the Revised Assessment in Neuro-Oncology (RANO) criteria are being increasingly used in the radiologic evaluation of response to treatment and tumor recurrence [5,6]. Temozolomide is an alkylating agent that methylates the DNA, thereby leading to an increase in the number of DNA strand breaks, that induces cellular apoptosis.

O6-Methylguanine-DNA-Methyltransferase (MGMT) promoter methylation testing has been shown to be an important prognostic factor [7,8]. The methylation of the MGMT promoter inhibits the repair of DNA damaged by temozolomide; thus, the lack of methylation may render tumor cells resistant to temozolamide [7]. Tumor biology has a key role in the resistance to drugs, hence in patient survival. The detection of imaging features that could identify tumor molecular biology characteristics has been analyzed in a number of recent studies, mostly to indicate the susceptibility of neoplasms to the available treatments. The importance of evaluating prognostic factors in cerebral glioma patients lies in the possibility of determining individualized treatment strategies [9-11].

The objective of this study was to assess the prognostic factors in malignant gliomas relying on the investigation of MGMT promoter methylation and establish a correlation with rCBV values obtained in the Perfusion-Weighted Image (PWI).

Materials and Methods


The study comprised 45 patients with grade III and IV gliomas based on World Health Organization (WHO) classification, treated from January 2010 through December 2013. All of the studied patients were initially treated with Temozolomide, in addition to surgery and radiation therapy. The study was approved by the research ethics committee and the patients signed informed consent forms.

The inclusion criteria were the following: age >18 years, preoperative perfusion MRI, histological assessment with mitotic index (Ki-67), MGMT promoter methylation evaluation, and a minimum follow-up of 12 months or until death. Surgical resection more than 90% estimated by two neuroradiologists was important inclusion criteria.

The exclusion criteria were the following: patients with severe comorbidities and short follow-up. Six patients were excluded for inadequate follow-up and histological profile. Patients undergoing biopsy or surgical resection of the primary lesion that were less than 90% were excluded from this study. Two patients with severe heart disease and another one patient with kidney problems were excluded from this study.

The clinical variables analyzed were age, sex, Karnofsky Performance Scale (KPS) score at the inception of treatment, occurrence of death, and survival time in months. The endpoint was death or the termination of the assessment when the time of follow-up was completed. Survival time was calculated in months. All patients were operated by the same neurosurgeon and gross total resection was the objective of the surgery.

Imaging studies

Patients underwent baseline MRI. New evaluations were performed on 1.5 and 3T GE imaging units (Milwaukee, WI) and included at least: sagittal T1-weighted, axial T2-weighted and FLAIR images; post gadolinium sagittal and axial T1-weighted images and DSC perfusion MRI study (Echo-planar GRE TR 2100ms, TE 80ms with 5-mm-thick sections, no gap, total of 17 sections, 35 repetitions). The contrast agent dose was 0.05 mmol/kg; infusion was performed using a power injector at the rate of 4 mL/s. The dynamic infusion was at all times preceded by one-fourth of the gadolinium dose in order to reduce the leakage effect. The perfusion maps were generated at GE AW Workstation 4.5 (Milwaukee, WI). The studies were reviewed by two Board-certified radiologists with more than five years of experience. The radiologists were blinded to the results of the MGMT promoter methylation and the histological assessment. The different types of MRI scanner did not affect the performance of perfusion.

The following variables were evaluated: lesion location, lesion size, pattern of contrast enhancement, tumor necrosis, rCBV measurement in the region of interest and dissemination of the lesion to the contralateral hemisphere or along the tracts. A threshold above 1.75 for rCBV was established for this sample to denote high perfusion [12].

Histological and MGMT promoter methylation status assessment

Tumor histology was analyzed by a team of qualified, independent pathologists. The following variables were described: degree of anaplasia according to the WHO criteria; mitotic index Ki- 67; presence, numerical values and classification of MGMT promoter methylation.

The assessment of the MGMT promoter methylation status was conducted using genomic DNA isolated from paraffin-embedded sections of tumor tissue. The details of these techniques have been published by Riemenscheneider et al. [13]. In order to estimate the percentage of MGMT promoter methylation in each sample, three separate readings were performed, and the mean was calculated. A minimum of five normal DNA samples collected from the blood of healthy volunteers were used as controls in each assessment [11].

Statistical analysis

Univariate analysis was performed in order to determine the initial relevance of the variables with respect to the prognosis of survival based on the endpoint death. The data were submitted to multivariate Cox regression analysis to establish the significant prognostic factors. The relative risk of death was determined for each significant variable in the multivariate analysis. The survival analysis of the methylated and unmethylated MGMT promoter groups was performed and evaluated by the log-rank test. A survival analysis relating MGMT promoter methylation to perfusion values was also performed, and the MGMT promoter methylation status was analyzed in relation to high or low levels of cerebral perfusion. The analysis of these data was conducted using the log-rank test. The second part of the statistical analysis was the assessment of the correlation between the imaging features defined as important according to the study design and the MGMT promoter methylation status. This analysis was performed using the chi-square test, with a p-value < 0.05 to denote statistical significance.


The assessment of MGMT promoter methylation was performed for 45 patients with malignant CNS gliomas who underwent surgery during the study period. Four were excluded from the study because they had a final histological diagnosis of oligodendroglioma, which changes the treatment response. Two other patients were excluded due to a short follow-up period. The mean age of the patients was 47 years old, with a predominance of male (Table 1). The mean KPS score of the patients was 70. The primary lesions were predominantly found in the frontal lobe, with 19 cases (Table 1). The tumor lesions were predominantly cortical in 29 patients. All patients studied in this series showed a resection of more than 90% of the primary lesion.