Table 2, Key Table.
Summary of studies that evaluate the prognostic or predictive value of MGMT protein or gene expressionin addition to promoter methylation status
| Study | Study goal relevant to this Opinion | Methods | Sample size | Relevant results | Conclusion | Reference |
|---|---|---|---|---|---|---|
| Lalezari et al. | To evaluate prognostic value of MGMT protein expression and optimize determination of MGMT status | Methylation: MSP Methylation: BiSEQ (cutoff: median number of methylated sites) Protein expression: IHC (cutoff: median) |
N=418 glioblastoma (IHC: 355, MSP: 02, BiSEQ: 312) | Multivariate analysis: Methylation by MSP is prognostic for OSa (p<0.0001c) and PFSb (p<0.0001) Methylation by BiSEQ is prognostic for OS (p<0.0001) and PFS (p=0.0006) Protein by IHC is prognostic for OS (p<0.0001) and PFS (p=0.001) Combination of methylation and low protein showed improved OS (p=0.0087) and PFS (p=0.0087) compared to other stratified groups |
Combined IHC and methylation analysis yields best assessment of MGMT status | [10] |
| Kreth et al. | To investigate prognostic and/or predictive value of MGMT mRNA expression | Methylation: MSP mRNA expression: qRT-PCR (cutoff: median) | N=63 (53 glioblastoma, 10 anaplastic astrocytoma) | Multivariate analysis: Methylation is prognostic for OS (p=0.0002) and PFS (p=0.0001) Low mRNA expression is prognostic for OS (p=0.0001) and PFS (p=0.0001) Notably, methylated tumors with high mRNA expression showed shorter OS (p<0.001) and PFS (p<0.001) than methylated tumors with low mRNA exp |
Methylation status alone is not sufficient for determining clinical outcome | [18] |
| Pandith et al. | To investigate the prognostic value of MGMT methylation and MGMT protein expression | Methylation: MSP Protein expression: IHC (cutoff: 10%) | N=63 (32 glioblastoma, 14 astrocytoma, 14 oligodendrogliom a, 3 other) | Multivariate analysis: MGMT promoter methylation was an independent prognostic factor (p<0.05) MGMT protein expression was an independent prognostic factor (p=0.002) Significant association between protein and patient outcome was found in groups treated with TMZ (p=0.040) and without TMZ (p=0.006) Significant association between promoter methylation and patient outcome was found in group treated with TMZ (p=0.029) but not without TMZ (p=0.706) |
Both methylation and protein expression should be evaluated | [29] |
| Uno et al. | To determine which method of evaluating MGMT status provides best prognostic and/or predictive value | Methylation: MSP Methylation: pyrosequencing (cutoff: 10%) mRNA expression: qRT-PCR (cutoff: median) Protein expression: IHC (cutoff: 10%) |
N=51 glioblastoma | Multivariate analysis: Only methylation by MSP (p=0.023) or pyrosequencing (p=0.005) was an independent prognostic factor | Promoter methylation status is a more reliable biomarker compared to mRNA or protein expression levels | [9] |
| Shah et al. | To correlate methylation and protein expression with clinical outcome | Methylation: MS- MLPA (3 region classification, cutoff: 0.1) Protein: IHC (cutoff: 15%) | N=70 glioblastoma (IHC: 31) | Multivariate analysis: Low protein expression was an independent predictive factor for PFS (p<0.0001) Methylation using 3R classification was an independent predictive factor for PFS (p<0.0001) |
Refinement of the best method to determine MGMT status is warranted | [11] |
| Cao et al. | To analyze the prognostic value of promoter methylation and protein expression | Methylation: MSP Protein expression: IHC (cutoff: 5%) |
N=83 glioblastoma (IHC: 80, MSP: 76, 73 with both IHC and MSP) | Univariate analysis: Methylation correlated with increased survival (p=0.014) Low protein expression was not prognostic (p=0.197) Notably, combination of methylation and low protein expression yielded longer survival compared to other subgroups (p=0.005) Multivariate analysis: best outcome in methylated- immunonegative compared to unmethylated- immunonegative (p=0.006) |
Combined evaluation of both Methylation status and negative protein expression may have more prognostic value |
[8] |
| Nagane et al. | To analyze the prognostic value of MGMT protein expression | Protein expression: Western blotting (cutoff: median) | N=30 glioblastoma (Western: 19, clinical outcome: 17) | Multivariate analysis: Low MGMT protein expression was an independent favorable prognostic factor for OS (p=0.040), but not PFS (p=0.060) | Low protein expression is a favorable prognostic factor for overall survival benefit in patients treated with TMZ | [41] |
| Sonoda et al. | To evaluate the prognostic value of MGMT promoter methylation and protein expression | Methylation: MSP Protein expression: IHC (cutoff: 20%) |
N=73 glioblastoma (MSP: 62) | Methylation (p=0.011) and negative expression (p=0.049) were independently associated with increased PFS, but not OS | Methylation and low expression are predictive markers for increased progression- free survival | [57] |
| Dahlrot et al. | To investigate the prognostic value of protein expression and combined evaluation of both protein and methylation status | Methylation: pyrosequencing (cutoff: 10%) Protein expression: double immunofluorescenc e assay (cutoff: median) |
N=171 glioblastoma (pyrosequencing: 157, expression: 171) | Univariate analysis: Low MGMT expression in tumor resulted in increased overall survival compared to high expression overall (p=0.01) and within the subgroup receiving the Stupp regimendd(p=0.001), but this trend in multivariate analysis was not significant (p=0.11) Notably, in the patient group who received the Stupp regimen, combined methylation and low expression resulted in the best prognosis, whereas unmethylated promoter and high expression showed the poorest prognosis (p=0.0002) |
Both methylation status and protein expression status are important to evaluate | [25] |
| Melguizo et al. | To investigate the prognostic value of MGMT promoter methylation and protein expression | Methylation: MSP Protein expression: IHC (cutoff: 25%) |
N=78 glioblastoma (methylation and protein expression: 76) | Univariate analysis: Methylation was significantly associated with increased PFS (p=0.036) and OS (p=0.031). Protein expression was not significantly correlated with PFS (0.712) or OS (p=0.894) | Methylation status, but not protein expression, has significant prognostic value | [16] |
| Karayan- Tapon et al. | To identify the method of determining MGMT status that has best prognostic value | Methylation: MSP Methylation: SQ- MSP (cutoff: median) Methylation: pyrosequencing (cutoff: median) mRNA expression: qRT-PCR (cutoff: median) Protein expression: IHC (cutoff: median) |
N=81 glioblastoma | Univariate analysis: Methylation by MSP (p=0.005), SQ-MSP (p<10−4), and pyrosequencing (p<10−4) was significantly associated with increased OS Low mRNA expression was significantly associated with increased OS (p=0.028) Protein expression was not significantly associated with OS (p=0.595) Multivariate analysis: Only methylation at CpG4 by pyrosequencing was a significant factor for predicting overall survival (p<0.0001) |
Methylation status is the best approach | [50] |
| Preusser et al. | To assess the value of MGMT by IHC as a clinical biomarker | Methylation: MSP Protein: IHC (cutoff: 10%, 50%) |
N=164 glioblastoma (MSP: 122) | Univariate analysis: Methylation by MSP was significantly associated with increased survival (p=0.0001) Protein expression was not significantly associated with clinical outcome at any tested cutoff value |
Protein expression by IHC is a less clinically useful biomarker than promoter methylation | [7] |
| Trabelsi et al. | To determine the best method for assessing MGMT methylation status | Methylation: MS- MLPA (cutoff: 0.25) and HM-450K Protein expression: IHC (cutoff: 10%) |
N=55 glioblastoma | Univariate analysis: All gene methylation by MS- MLPA was significantly associated with increased overall survival (p=0.021) and relapse-free survival (p=0.02) in all glioblastoma and in TMZ- treated group (p=0.022 and p- 0.017, respectively) Promoter methylation by MS- MLPA was significantly associated with overall survival in TMZ-treated group (p=0.046), but not RFS No significant correlation was found between survival and expression by IHC, or methylation by HM-450K (small sample size for HM- 450K) |
MGMT methylation has predictive value | [58] |
| Hsu et al. | To compare the prognostic value of MGMT status by four different methods | Methylation: MSP, qMSP (cutoff: median), pyrosequencing (cutoff: 5%) Protein expression: IHC (cutoff: 10%) |
N=121 glioblastoma | Multivariate analysis: All methods had prognostic value for PFS and OS, respectively, including IHC- (p=0.003, p=0.047), MSP+ (p=0.002, p=0.001), qMSP+ (p=0.002, p=0.001), PSQ+ (p<0.001, p=0.001) Notably, patients with IHC- negative/methylation-positive tumors showed increased PFS and OS compared to those with IHC-positive/methylation- negative; further, the addition of pyrosequencing significantly improved prediction of prognosis in IHC-negative cases |
All methods were significantly associated with clinical outcome, and addition of methylation status evaluation may enhance the predictive power of IHC for some patients |
[49] |
a)
OS = overall surviva
b)
PFS = progression-free survival
c)
Statistical significance indicated by p<0.05
d)
Stupp regimen = protocol of glioblastoma treatment with radiation therapy and concomitant and adjuvant temozolomide