Methylation of O6-Methylguanine-Methyltransferase (MGMT)
Description
O6-Methylguanine-Methyltransferase (MGMT) is an enzyme in cells that repairs DNA. Methylation of the MGMT gene reduces production of the MGMT enzyme and the ability of tumor cells to repair damage caused by chemotherapy. Methylation of MGMT is a prognostic and predictive factor for high grade gliomas.
O6-Methylguanine-Methyltransferase (MGMT) is an enzyme in cells that repairs DNA. DNA repair is undesirable in tumors, because it may enable them to overcome the DNA damage done by chemotherapy. With methylation, less MGMT enzyme is produced, which may lead to prolonged survival compared to unmethylated MGMT.
A patient with increased MGMT methylation is more likely to respond to alkylating agents such as temozolomide (Temodar) and the nitrosoureas, some of the few drugs effective for brain tumors. MGMT methylation is a special (not routine) molecular test done on tumor tissue. It is used primarily for anaplastic oligodendroglioma, anaplastic astrocytoma and glioblastoma multiforme, but can also be done for low grade malignant central nervous system tumors.
Rationale
Methylation of O6-Methylguanine-Methyltransferase (MGMT) is a Registry Data Collection Variable in AJCC. It was previously collected as Brain, CS SSF #4.
Additional Info
**Source documents:** pathology report, specialty, or reference laboratory report
**Other names include** MGMT promoter methylation, methylation status
Notes
**Note 1:** **Physician Statement**
* Physician statement of the methylation status of the MGMT, also termed MGMT promoter, gene can be used to code this data item when no other information is available.
**Note 2:** **Applicable histologies**
* Below is a list of histologies/terms for which the MGMT test is commonly done. If the test was done, record the results, regardless of the histology. If the histology is not listed among those for which the MGMT test is commonly done, and the test result is not readily available, assume it was not done and code 9 for unknown.
* 9382/3: Anaplastic oligoastrocytoma, NOS
* 9382/3: Oligoastrocytoma, NOS
* 9400/3: Diffuse astrocytoma (IDH mutant, IDH wild type, NOS)
* 9401/3: Anaplastic astrocytoma (IDH mutant, IDH wild type, NOS)
* 9411/3: Gemistocytic astrocytoma, IDH mutant
* 9424/3: Anaplastic pleomorphic xanthoastrocytoma
* 9440/3: Glioblastoma (epithelioid, IDH wild type, NOS)
* 9441/3: Giant cell glioblastoma
* 9442/3: Gliosarcoma
* 9445/3: Glioblastoma, IDH mutant
* 9450/3: Oligodendroglioma (IDH mutant and 1p/19q codeleted, NOS)
* 9451/3: Anaplastic oligodendroglioma (IDH mutant and 1p/19 codeleted, NOS)
* 9505/3: Anaplastic ganglioglioma
* 9530/3: Anaplastic (malignant)meningioma
Coding Guidelines
**1)** **Code 0** when the MGMT is not identified/not present
**2)** **Code 1** when the MGMT is low
**3)** **Code 2** when the MGMT is high
**4)** **Code 3** when the MGMT is mentioned, but not stated as low or high
**5)** **Code 6** for a **Benign (/0)** or **Borderline (/1) tumor**
**6)** **Code 9** when
* **a.** No information in the medical record about MGMT
* **b.** MGMT test not done (not assessed)
* **c.** Unknown if MGMT test was performed (unknown if assessed)
Default
8
Metadata
SSDI
| Code |
Description |
| 0 |
MGMT methylation absent/not present, unmethylated MGMT |
| 1 |
MGMT methylation present, low level
Hypomethylated
Partial methylated |
| 2 |
MGMT methylation present, high level
Hypermethylated |
| 3 |
MGMT methylation present, level unspecified |
| 6 |
Benign or borderline tumor |
| 7 |
Test ordered, result not in chart |
| 8 |
Not applicable: Information not collected for this case
(If this item is required by your standard setter, use of code 8 will result in an edit error.) |
| 9 |
Not documented in medical record
Cannot be determined by the pathologist
MGMT not assessed or unknown if assessed |
