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Posttreatment Effect of MGMT Methylation Level on Glioblastoma Survival

Rikke H Dahlrot1, Pia Larsen2, Henning B Boldt3

  • 1Department of Oncology, Odense University Hospital.

Journal of Neuropathology and Experimental Neurology
|May 7, 2019
PubMed

Insights

O6-methylguanine-DNA methyltransferase (MGMT) methylation levels impact glioblastoma survival, particularly after 9 months. Higher MGMT methylation significantly benefits patients surviving beyond this crucial period.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • O6-methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein crucial for cellular response to alkylating agents like temozolomide.
  • MGMT's role in glioblastoma (GBM) prognosis is established, but its methylation's time-dependent prognostic effect requires further investigation.

Purpose of the Study:

  • To investigate the prognostic impact of MGMT methylation levels on overall survival (OS) and progression-free survival (PFS) in primary glioblastoma patients.
  • To analyze the time-varying effects of MGMT methylation on OS using advanced statistical modeling.

Main Methods:

  • Pyrosequencing was used to determine MGMT methylation levels at 4 CpG sites in 327 primary glioblastoma patients.
  • Cox proportional hazards models, including an extension for time-varying effects, were employed to assess the association between MGMT methylation and survival outcomes.

Main Results:

  • MGMT methylation level showed a significant association with OS starting around 9 months post-diagnosis, but not before.
  • For patients surviving ≥9 months, even minor increases in MGMT methylation were associated with improved OS (HR=0.97, 95% CI [0.96, 0.98]).
  • The predictive accuracy (Harrel's C) of MGMT methylation for OS from 9 months onwards was 66%.

Conclusions:

  • MGMT methylation is a strong prognostic marker for glioblastoma survival, but its effect is time-dependent, becoming significant around 9 months after diagnosis.
  • Beneficial effects of MGMT methylation on survival are observed at levels lower than previously considered, highlighting its prognostic potential.
  • Future prognostic evaluations should incorporate the time-varying nature of MGMT methylation's effect on overall survival.
Keywords:
Epigenetic marker prognosticGlioblastomaO6-methylguanine-DNA methyltransferase (MGMT)SurvivalTime-varying effect

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