DISTRIBUTION AND IMAGING CHARACTERISTICS OF HIGH-GRADE GLIOMAS ACCORDING TO METHYLATION STATUS OF MGMT GENE PROMOTER

Background: Many molecular investigations have identified that the methylation status of the O-6-methylguanine-DNA methyl transferase (MGMT) gene promoter in patients with high grade glioma is associated with a improved prognosis and survival when treated with temozolamide (TMZ).

Aims and Objective: The aim of the study was to find out the distribution of methylation status and imaging characteristics in patients with High Grade Gliomas.

Method: The study included forty consecutive patients who presented with neurological symptoms and were subsequently diagnosed as having a primary brain tumour on conventional MRI scan. MR-perfusion imaging was performed to determine the grade of the tumor which was subsequently compared with histopathological grade of the tumor after brain biopsy. The biopsy or surgical specimens were further analysed for determining the MGMT promoter methylation status using Methylation-specific PCR (MSP).

Results: The mean age of patients was 50.3 years in the methylated group and 49.1 years in the unmethylated group (p value = 0.671). Out of 40 patients, 18 had methylated MGMT promoters while 22 had unmethylated MGMT promoters. We found that ring-like enhancement was seen more frequently in the unmethylated tumours (72.7%) than in methylated ones (61.1%). The presence of T₂ heterogeneous signal intensity was seen more in the methylated group (77.8%) than unmethylated group (68.2%). Severe necrosis (affecting >50% of the tumour) was seen more in the methylated tumours (61.1%) than in the unmethylated tumours (40.09%). However, these differences were found to be statistically insignificant.

Conclusion: The distribution and imaging characteristics may provide some information about methylation of high-grade gliomas but a multicentric large data maybe required to reach a consensus about its reliability when biopsy of the methylation status of the tumour is not available.