Glioblastoma multiforme (GBM) is the most common and most malignant primary brain tumor in adults with an incidence of 3-4/100,000/year. The median survival of patients with GBM is 12.1–14.6 months [
We performed a retrospective study of 44 patients with a diagnosis of WHO grade IV astrocytoma—GBM (
Glioblastoma patient demographics and clinical characteristics.
Patient characteristics | |
---|---|
Sex | |
Male to female | 1 |
Male | 22 |
Female | 22 |
Age, years | |
Median | 64.3 |
Range | 35–87 |
KPS | |
Median | 77.5 |
Range | 30–100 |
Postoperative treatment | |
RT (±CT) | 29 |
CT alone | 1 |
None | 15 |
KPS: Karnofsky performance score; RT: radiotherapy; CT: chemotherapy.
DNA was extracted from 10
For detection of mutant allele IDH1 c.395G>A (p.R132H, COSMIC ID 28746), we use TaqMan Mutation Detection Assays (assay name: IDH1 28746 mu and IDH1 rf) with the TaqMan Mutation Detection IPC Reagent Kit (Life Technologies, Carlsbad, California, USA). Mutant allele detection we performed according to recommended procedure and reaction conditions is found in the manual. For the amplification, we used the Stratagene Mx3000P real-time PCR system instrument (Agilent Technologies, Inc., Santa Clara, CA, USA). Detection of mutant alleles was performed in duplicate in a reaction volume of 20 µL. Detection of reference gene was also performed in duplicate. The analysis of the positive samples was repeated. Before analysis of our collection of tumor samples, we analyzed samples of normal brain tissue for detection of cut-off amplification curve. No amplification of mutant allele was present in normal brain tissue. On the basis of these results and the shape of amplification curve of positive tumor samples, we determined the ΔCt cut-off 25 value.
Overall survival (OS) was defined as the time between the diagnosis and death or last follow-up. Progression-free survival (PFS) was defined as the time between the diagnosis and recurrence or last follow-up. Kaplan-Meier survival curves were plotted and the survival distributions were compared with the use of the Wilcoxon test. Reported
The examined mutation IDH1 R132H was observed in 20 of 44 GBM-patient tumor samples. Therefore we identified the IDH1 mutation in more than 45.4% of glioblastomas. The separation of primary and secondary glioblastomas (GBM that progressed from the low-grade glioma) was done on the basis of clinically relevant information, where possible. The IDH1 R132H mutation occurred in 4 of 26 primary GBMs (15.3%), whereas the majority, 16 of 18 (89.9%) were of secondary glioblastomas mutated (Table
The representation of IDH1 R132H mutation in primary versus secondary glioblastomas.
Glioblastoma type | Primary GBM ( |
Secondary GBM ( |
---|---|---|
Mutation status [ |
||
IDH1 R132H | 4 (15.3%) | 16 (89.9%) |
IDH1 wild-type | 22 (84.7%) | 2 (11.1%) |
Results for progression-free survival and overall survival differences in patients with GBM in relation to IDH1 mutation status.
Glioblastoma results |
|
Median [days] (95% Cl) |
|
---|---|---|---|
Overall survival (OS) | |||
IDH1 R132H | 20 | 270 (139–400) | 0.024 |
IDH1 wild-type | 24 | 130 (87–172) | |
Progression-free survival (PFS) | |||
IDH1 R132H | 20 | 136 (22–249) | 0.021 |
IDH1 wild-type | 24 | 51 (19–82) |
Progression-free survival of patients with glioblastoma with (red line) or without (blue line) IDH1 R132H gene mutation.
Overall survival of patients with glioblastoma with (red line) or without (blue line) IDH1 R132H gene mutation.
Recurrent IDH mutations and their role in oncogenesis and tumor progression were described for the first time in GBM [
The representation of IDH1 mutations in various cancers [
The representation of IDH1 mutations in various types of central nervous system tumors [
The fundamental shift in the understanding of mutated IDH and its role in cancer progression came with the observation of the neomorphic function of the mutated enzyme. Instead of the production of alpha-ketoglutarate, mutated IDH1 produced novel oncometabolite 2-hydroxyglutarate (2-HG) that was highly accumulated in the cancer cells [
Mutations in IDH1 are important also for their clinical consequences. Recent studies revealed the important role of mutated IDH1 in the assessment of astrocytoma patient prognosis. Therefore IDH1 mutations could serve in the near future as the standard prognostic biomarkers for patients with grade II, III, and IV astrocytomas. The differences in OS between IDH1-mutant and IDH1 wildtype GBM were 3.8 versus 1.1 years [
The results from our study also support the IDH1 mutation R132H to be the strong prognostic factor for patients with GBM. Although the differences in median PFS and OS between patients with IDH1 mutated and IDH1 wild-type tumors are not as big as in other studies, they are statistically significant. One reason for the relatively small differences in median PFS and OS between both groups could be the heterogeneity of the treatment protocols. The standard treatment with neurosurgery and concomitant chemo-radiotherapy with temozolomide was implemented in 29 patients and 1 patient had only radiotherapy and 15 patients were treated neither with radiotherapy nor with chemotherapy (Table
The recent study of mutations in telomerase reverse transcriptase (TERT) gene promoter has revealed the high incidence of these aberrations in a large portion of primary GBMs (about 80%) [
Despite the drawbacks of our study mentioned above, IDH1 R132H mutation still serves as a strong prognostic biomarker for our patients with GBM.
The IDH1 R132H mutation was observed in the interestingly higher number of patients with GBM that was previously published by other groups. On the other hand, the majority of mutated GBMs in our cohort are probably secondary glioblastomas. The prognostic value of the IDH1 R132H mutation was also observed. Patients with this mutation had significantly longer PFS as well as OS than patients with wild-type IDH1. The IDH1 mutation status could be used as a strong prognostic factor for patients with GBM, but further validation of this biomarker in large prospective clinical trials is urgently needed.
The authors declare that they have no conflict of interests regarding the publication of this paper.
This work was supported by MH CZ-DRO (Faculty Hospital in Plzen—FNPl, 00669806) and the project ED2.1.00/03.0076 from European Regional Development Fund.