Aim: MGMT promoter methylation has been associated with improved survival in glioblastoma multiforme treated with temozolomide. However, there is no consensus on specific cut-off levels of methylation. The aims of the study were to explore the prognostic impact of MGMT methylation status and to analyze the role of specific cut-off values.
Materials & methods: We analyzed 108 glioblastoma multiforme patients treated between 2008 and 2013 stratified according to three pyrosequencing-based quantitative methylation in: unmethylated (methylation <9%), intermediate (9-29%) and highly methylated (>29%).
Results: The three-class stratification has a prognostic impact (median progression-free survival: 7.97, 11.6 and 15 months respectively; p = 0.004; median OS: 13.2, 15.8 and 19.5 months, respectively; p = 0.0002), especially in patients exposed to temozolomide.
Conclusion: Our study confirmed that the independent prognostic role of MGMT methylation status. An average level of methylation between all investigated CpGs of 9% may help discriminating between methylated and unmethylated tumors.
Keywords: CpG islands; IDH1; MGMT; cut-off; glioblastoma; methylation; pyrosequencing; temozolomide.