UC Irvine

Abstract

OBJECTIVE

To correlate the percentage of MGMT methylation with progression-free survival (PFS) and overall survival (OS) in GBM patients receiving alkylating chemotherapy.

BACKGROUND

MGMT promoter methylation is a known favorable factor for patients with GBM to have better response to the treatment with alkylating chemotherapy and better survival outcome. However, in daily practice, patients with very high percentage of MGMT methylation sometimes were observed to have a shorter survival period. This study is to investigate if the strength of the positivity is correlated to the PFS and OS in GBM patients receiving alkylating chemotherapy. METHODS and PATIENTS: Quantitative MGMT methylation measurement was performed. 5% was defined as positive methylation. Seventeen patients with a diagnosis of GBM and methylated MGMT were reviewed retrospectively. Patients were placed into 3 categories based on their MGMT methylation percentages: 5–33%, 34–66%, and 67–100%. The average PFS and OS were calculated for each category.

RESULTS

The 6 patients in the 5–33% methylation category had an average PFS of 14.8 months (range 9 to 32) and OS of 27.2 months (range 10 to 42). The 8 patients in the 34–66% methylation category had an average PFS of 23.9 months (range 0 to 73) and OS of 28.1 months (range 1 to 82). The 3 patients in the 67–100% methylation category had an average PFS of 9.6 months (range 2 to 21) and censored OS of 14.7 months (range 2 to 35) as 2 of the 3 are alive.

CONCLUSION

Our sample size is too small to provide conclusions. Comparing the first two methylation categories, the extent of MGMT methylation appears positively correlates with PFS (14.8 versus 23.9 months) but not OS of patients (27.2 versus 28.1 months). Data from additional 15 MGMT methylated patients after follow-ups will be added for analysis.