INTRODUCTION Quantitative methylation specific PCR (qMSP) is a frequently used technique to assess MGMT gene promoter methylation in glioblastoma patients. The optimal technical cut-off value to distinguish methylated from unmethylated samples is nevertheless still undetermined. In literature, a "grey zone" of diagnostic uncertainty has been described. METHODS We performed a retrospective analysis of newly diagnosed glioblastoma patients treated according to the Stupp protocol. Epidemiological data were gathered from the individual patient files. MGMT gene promoter methylation status was determined on stored tumour samples using qMSP. A strong, weak or absent promoter methylation was determined based on Cq values (quantification value) of the MGMT and ACTB primers as well as a positive control sample. RESULTS In total, 181 patient files were reviewed and included for statistical analysis. MGMT promoter hypermethylation was detected in 38.7% of glioblastoma patients. The median overall survival of unmethylated and strongly methylated patients was 10.1 months and 19.7 months respectively. Furthermore, 11% of the total patient cohort had a weak MGMT gene promoter methylation. The median OS in this subgroup was 15.4 months, significantly better compared to the unmethylated cohort (P < 0.001). Multivariate Cox regression analysis showed weak MGMT promoter methylation as an independent prognostic parameter for overall survival. CONCLUSION Glioblastoma patients with weak promoter methylation show a statistically significant longer overall survival when compared to clearly unmethylated patients. Patients with grey zone qMSP test results should receive additional molecular analysis in future to further direct individual therapy strategies.

中文翻译：

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MGMT基因启动子甲基化弱可为新诊断成胶质母细胞瘤的患者带来临床上显着的生存获益：一项回顾性队列研究。

引言定量甲基化特异性PCR（qMSP）是评估胶质母细胞瘤患者MGMT基因启动子甲基化的常用技术。然而，仍然无法确定区分甲基化样品和未甲基化样品的最佳技术临界值。在文献中，已经描述了诊断不确定性的“灰色区域”。方法我们对根据Stupp方案治疗的新诊断的胶质母细胞瘤患者进行了回顾性分析。流行病学数据是从各个患者档案中收集的。使用qMSP在储存的肿瘤样品上确定了MGMT基因启动子的甲基化状态。基于MGMT和ACTB引物以及阳性对照样品的Cq值（量化值）确定强，弱或不存在启动子甲基化。结果总计 审查了181个患者档案，并进行了统计分析。在38.7％的胶质母细胞瘤患者中检测到了MGMT启动子的高甲基化。未甲基化和强甲基化患者的中位总生存期分别为10.1个月和19.7个月。此外，全部患者队列中有11％的MGMT基因启动子甲基化较弱。该亚组的中位OS为15.4个月，与未甲基化队列相比显着改善（P <0.001）。多元Cox回归分析显示，MGMT启动子甲基化较弱，是整体生存的独立预后参数。结论与明显未甲基化的患者相比，启动子甲基化较弱的胶质母细胞瘤患者在统计学上具有更长的总生存期。