# MGMT promoter methylation

Source: https://onco.cc/biomarkers/mgmt-promoter-methylation/  
OnCo record `mgmt-promoter-methylation` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Methylation of the MGMT promoter switches off the repair enzyme that undoes temozolomide's damage. Methylated glioblastomas live longer on temozolomide; unmethylated ones gain little, and trials now use the result to spare or intensify chemotherapy.

## Summary

Methylation-specific PCR, pyrosequencing or methylation arrays report the promoter as methylated or unmethylated, with laboratory-specific cut-offs (pyrosequencing commonly 10 percent). The temozolomide (Temodar) label for newly diagnosed glioblastoma does not require MGMT testing; the EORTC/NCIC trial that established the regimen showed the survival benefit concentrated in methylated tumours (Hegi et al., NEJM 2005), and EANO and NCCN guidelines recommend testing, with omission of temozolomide an option for elderly patients with unmethylated tumours. The CeTeG/NOA-09 trial (NCT01149109) tested lomustine plus temozolomide only in methylated glioblastoma.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: MGMT methylation; MGMT methylated; MGMT promoter methylated; MGMT unmethylated; methylated MGMT; MGMT status
- Tags: biomarker; methylation; no-approval

## Sources

- Hegi et al. 2005: https://doi.org/10.1056/NEJMoa043331
- TEMODAR prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=046a9011-3911-4d3f-a15f-fbb56d5aad56

## Connected records

- biomarkers: [1p/19q codeletion](https://onco.cc/biomarkers/1p19q-codeletion-readout/), [H3 K27M mutation](https://onco.cc/biomarkers/h3-k27m/), [IDH1 R132 mutation](https://onco.cc/biomarkers/idh1-r132/)
- cancers: [Astrocytoma, IDH-mutant (grades 2 to 4)](https://onco.cc/cancers/idh-mutant-astrocytoma/), [Glioma & glioblastoma](https://onco.cc/cancers/glioblastoma/)
- drugs: [Temozolomide](https://onco.cc/drugs/temozolomide/)
- terms: [Alkylating agents and antimetabolites](https://onco.cc/terms/alkylating-agent/), [MGMT promoter methylation](https://onco.cc/terms/mgmt/)
- targets: [MGMT (O6-methylguanine-DNA methyltransferase)](https://onco.cc/targets/mgmt-protein/)

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JSON: https://onco.cc/api/v1/entities/mgmt-promoter-methylation.json