Oligodendroglioma Patients Research Articles

Transformation of low grade glioma and correlation with outcome: an NCCTG database analysis

Glioblastomas (GBM) may originate de novo (primary), or following transformation from a lower grade glioma (secondary), and it has been postulated that these tumors may have different biological behaviors. We performed a correlative analysis involving 204 patients with glioma treated prospectively on NCCTG clinical trials. Central pathology review of tumor tissues taken at the time of initial diagnosis and at recurrence were performed in all patients. Tumors progressed from low (WHO grade 2) to high (grade 3-4) at recurrence in 45% low grade oligodendroglioma patients, in 70% with low grade oligoastrocytoma, and 74% with low grade astrocytoma (P = 0.031). Median overall survival (OS) from initial diagnosis varied by histology: oligodendroglioma, 8.8 years; (95% CI 5.7-10.2); oligoastrocytoma, 4.4 years (95% CI 3.5-5.6); astrocytoma grade 2 3.1 years (astrocytoma grade 2-4, 2.1 years) (95% CI 1.7-2.5, P < 0.001). Mean time to recurrence (TTR) also varied between patients with de novo GBM, those secondary GBM, and those that remained non-GBM at recurrence (1.1 ± 1.1 vs. 2.9 ± 1.8 vs. 4.0 ± 2.9 years, respectively, P < 0.001). Median OS from time of recurrence also varied between these three categories (0.7 years, 95% CI: 0.5-1.1 vs. 0.6 years, CI: 0.5-1.0 vs. 1.4 years, 95% CI: 1.1-2.0, respectively) (P < 0.001). At time of relapse, transformation to higher grade is frequent in low grade pure and mixed astrocytomas, but is observed in less than half of those with low grade oligodendroglioma. From time of recurrence, OS was not significantly different for those with primary versus secondary GBM, and it may thus be reasonable include patients with secondary GBM in clinical therapeutic trials for recurrent disease.

IDH1 and IDH2 Mutations Are Prognostic but not Predictive for Outcome in Anaplastic Oligodendroglial Tumors: A Report of the European Organization for Research and Treatment of Cancer Brain Tumor Group

Recent studies have shown the prognostic significance of IDH1 mutations in glioma. It is yet unclear if IDH1 mutations are predictive for outcome to chemotherapy. We determined the effect of IDH1 mutations on progression-free survival and overall survival (OS), and its correlation with other clinical and molecular features in the prospective randomized European Organization for Research and Treatment of Cancer study 26951 on adjuvant procarbazine, 1-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea, and vincristine (PCV) in anaplastic oligodendroglioma. IDH1 and IDH2 alterations of the mutational hotspot codons R132 and R172 were assessed by the bidirectional cycle sequencing of PCR-amplified fragments. MGMT promoter methylation was assessed using methylation-specific multiplex ligation-dependant probe amplification based on methylation-sensitive restriction analysis. Loss of chromosomes 1p, 19q, 10, and 10q and the gain of 7 and the EGFR gene were assessed with fluorescence in situ hybridization. From 159 patients, sufficient material was available for IDH1 analysis. In 151 and 118 of these patients, respectively, the 1p/19q status and the MGMT promoter methylation status were known. In 73 cases (46%), an IDH1 mutation was found and only one IDH2 mutation was identified. The presence of IDH1 mutations correlated with 1p/19q codeletion and MGMT promoter methylation, and inversely correlated with loss of chromosome 10, EGFR amplification, polysomy of chromosome 7, and the presence of necrosis. IDH1 mutations were found to be prognostic in the radiotherapy- and the radiotherapy/PCV-treated patients, for both progression-free survival and OS. With Cox proportional hazard modeling for OS with stepwise selection, IDH1 mutations and 1p/19q codeletion but not MGMT promoter methylation were independent prognostic factors. In this homogeneously treated group of anaplastic oligodendroglioma patients, the presence of IDH1 mutations was found to carry a very strong prognostic significance for OS but without evidence of a predictive significance for outcome to PCV chemotherapy. IDH1 mutations were strongly associated with 1p/19q codeletion and MGMT promoter methylation.

Long-term Temozolomide Treatment Induces Marked Amino Metabolism Modifications and an Increase in TMZ Sensitivity in Hs683 Oligodendroglioma Cells

Gliomas account for more than 50% of all primary brain tumors. The worst prognosis is associated with gliomas of astrocytic origin, whereas gliomas with an oligodendroglial origin offer higher sensitivity to chemotherapy, especially when oligodendroglioma cells display 1p19q deletions. Temozolomide (TMZ) provides therapeutic benefits and is commonly used with radiotherapy in highly malignant astrocytic tumors, including glioblastomas. The actual benefits of TMZ during long-term treatment in oligodendroglioma patients have not yet been clearly defined. In this study, we have investigated the effects of such a long-term TMZ treatment in the unique Hs683 oligodendroglioma model. We have observed increased TMZ sensitivity of Hs683 orthotopic tumors that were previously treated in vitro with months of progressive exposure to increasing TMZ concentrations before being xenografted into the brains of immunocompromised mice. Whole-genome and proteomic analyses have revealed that this increased TMZ sensitivity of Hs683 oligodendroglioma cells previously treated for long periods with TMZ can be explained, at least partly, by a TMZ-induced p38-dependant dormancy state, which in turn resulted in changes in amino acid metabolism balance, in growth delay, and in a decrease in Hs683 oligodendroglioma cell-invasive properties. Thus, long-term TMZ treatment seems beneficial in this Hs683 oligodendroglioma model, which revealed itself unable to develop resistance against TMZ.

Genetic markers in oligodendroglial tumours

BackgroundOliogodendrogliomas are brain tumours composed of the cells resembling oligodendrocytes. They represent the third most common glial tumour, comprising 2.5% of all primary brain tumours and 5–20% of all gliomas.ConclusionsOligodendroglial tumours with 1p and 19q loss demonstrate a better overall prognosis due to more indolent clinical behaviour and higher sensitivity to treatment. Additionally, 1p and 19q loss is a marker of clinical utility, helping to assess tumour sensitivity to chemotherapy and harbouring the potential for improving the diagnosis and survival of oligodendroglioma patients as well as future clinical practice.

High-grade gliomas in survivors of childhood acute lymphoblastic leukaemia

Dear Editor: We read with great interest the recent article by Bien et al. on high-grade gliomas that occurred in children cured of acute lymphoblastic leukaemia (ALL). In this study, the authors reported two cases of glioblastoma multiforme and one case of anaplastic astrocytoma with poor overall survival despite aggressive treatment. Cranial irradiation has been considered as the most important factor for the development of secondary brain tumours. The authors concluded that early detection followed by complete resection and chemoradiotherapy is of paramount importance; however, they do not warrant better prognosis [1]. We recently studied the secondary malignant brain tumours in children who were previously treated for ALL in our institute and we encountered one case of glioblastoma multiforme and two cases of anaplastic oligodendrogliomas. The tumours developed after a mean period of 6.8 years after ALL treatment. The occurrence of anaplastic oligodendrogliomas is exceedingly rare and only eight cases have been reported in the literature. For further investigation, we undertook a molecular cytogenetic study of the oligodendroglioma specimens obtained from the two patients using fluorescence in situ hybridization (FISH) with DNA probes mapping to chromosome 1p36, 19p13 and 19q13. FISH analysis demonstrated in both cases 1p36 deletions (unpublished data). Studies of oligodendroglioma patients indicated that a loss of chromosome 1p and 19q was associated with high sensitivity to chemotherapy and radiotherapy and a better probability of survival [2]. We believe that it would be interesting to investigate if the allelic loss differs from those observed in primary lesions. Further research is needed to clarify if certain underlying genetic characteristics may also be associated with an increased risk of radiation-induced brain tumours.

Cytoplasmic LRIG2 expression is associated with poor oligodendroglioma patient survival

The three leucine-rich repeats and immunoglobulin-like domains (LRIG) genes encode integral membrane proteins. Of these, LRIG1 negatively regulates growth factor signaling and is implicated as a tumor suppressor in certain malignancies. In astrocytic tumors, the subcellular distribution of LRIG proteins is associated with specific clinicopathological features and patient survival. The role of LRIG proteins in oligodendroglioma has not previously been studied. Here we used immunohistochemistry to analyze the expression of the LRIG proteins in 63 oligodendroglial tumors, and evaluated possible associations between LRIG protein expression and clinicopathological parameters. Notably, cytoplasmic LRIG2 expression was found to be an independent prognostic factor associated with poor oligodendroglioma patient survival. This is the first report of an LRIG protein showing a negative effect on survival, suggesting that LRIG2 might have a function different from that of LRIG1, and possibly contributing to the etiology of oligodendroglioma.

Frequent biallelic inactivation and transcriptional silencing of the DIRAS3 gene at 1p31 in oligodendroglial tumors with 1p loss

Deletion of the short arm of chromosome 1 is common in oligodendroglial tumors and has been identified as a powerful molecular marker for response to radio- and chemotherapy as well as favorable prognosis. Here, we investigated a series of 59 human primary gliomas for aberrations of the DIRAS3 (ARHI) gene, a maternally imprinted RAS-related tumor suppressor at 1p31. We found that DIRAS3 mRNA expression levels were significantly decreased in oligodendrogliomas with 1p deletion when compared to tumors with retention on 1p. While mutational analysis yielded no tumor-associated mutations, assessment of the methylation status of DIRAS3 showed biallelic DIRAS3 inactivation due to methylation of the retained allele in 95% of oligodendrogliomas (19 out of 20) with 1p deletions. In contrast, only 28% of oligodendrogliomas (5 out of 18) without 1p deletions and less than 5% of astrocytic tumors (1 out 21) had biallelic inactivation, i.e., methylation of both DIRAS3 alleles. Furthermore, in oligodendroglioma patients biallelic DIRAS3 inactivation was significantly associated with low DIRAS3 transcripts levels and longer overall survival. Taken together, our data suggest DIRAS3 as a novel, prognostically relevant candidate gene that is frequently methylated and silenced in oligodendroglial tumors with 1p deletion.

Loss of NOTCH2 Positively Predicts Survival in Subgroups of Human Glial Brain Tumors

The structural complexity of chromosome 1p centromeric region has been an obstacle for fine mapping of tumor suppressor genes in this area. Loss of heterozygosity (LOH) on chromosome 1p is associated with the longer survival of oligodendroglioma (OD) patients. To test the clinical relevance of 1p loss in glioblastomas (GBM) patients and identifiy the underlying tumor suppressor locus, we constructed a somatic deletion map on chromosome 1p in 26 OG and 118 GBM. Deletion hotspots at 4 microsatellite markers located at 1p36.3, 1p36.1, 1p22 and 1p11 defined 10 distinct haplotypes that were related to patient survival. We found that loss of 1p centromeric marker D1S2696 within NOTCH2 intron 12 was associated with favorable prognosis in OD (P = 0.0007) as well as in GBM (P = 0.0175), while 19q loss, concomitant with 1p LOH in OD, had no influence on GBM survival (P = 0.918). Assessment of the intra-chromosomal ratio between NOTCH2 and its 1q21 pericentric duplication N2N (N2/N2N-test) allowed delineation of a consistent centromeric breakpoint in OD that also contained a minimally lost area in GBM. OD and GBM showed distinct deletion patterns that converged to the NOTCH2 gene in both glioma subtypes. Moreover, the N2/N2N-test disclosed homozygous deletions of NOTCH2 in primary OD. The N2/N2N test distinguished OD from GBM with a specificity of 100% and a sensitivity of 97%. Combined assessment of NOTCH2 genetic markers D1S2696 and N2/N2N predicted 24-month survival with an accuracy (0.925) that is equivalent to histological classification combined with the D1S2696 status (0.954) and higher than current genetic evaluation by 1p/19q LOH (0.762). Our data propose NOTCH2 as a powerful new molecular test to detect prognostically favorable gliomas.

Association between Functional EGF+61 Polymorphism and Glioma Risk

Epidermal growth factor (EGF) plays a critical role in cancer. A polymorphism in the EGF gene (EGF+61) may influence its expression and contribute to cancer predisposition and aggressiveness. In the present study, we aimed to elucidate the role of EGF+61 in glioma susceptibility and prognosis. A case-control study involving 197 glioma patients and 570 controls was done. Univariate and multivariate logistic regression analyses were used to calculate odds ratio (OR) and 95% confidence intervals (95% CI). False-positive report probability was also assessed. The luciferase reporter gene assay was used to ascertain the functional consequences of this polymorphism. Corroborating the univariate analysis, the multivariate model showed that the G allele conferred higher risks for gliomas (OR, 1.32; 95% CI, 1.04-1.67), glioblastomas (OR, 1.47; 95% CI, 1.02-2.10), and oligodendrogliomas (OR, 1.55; 95% CI, 1.07-2.23). The GG genotypes were associated with increased risk for gliomas (OR, 1.71; 95% CI, 1.07-2.73), glioblastomas (OR, 2.03; 95% CI, 1.02-4.05), and oligodendrogliomas (OR, 2.72; 95% CI, 1.18-6.28). In addition, the AG+GG genotypes were associated with higher risk for gliomas (OR, 1.52; 95% CI, 1.03-2.23) and oligodendrogliomas (OR, 2.80; 95% CI, 1.35-5.79). No significant association was observed between the EGF+61 polymorphism and glioblastoma or oligodendroglioma patients' overall survival. The luciferase reporter gene assay exhibited a significant increased promoter activity for the G variant compared with the reference A allele. These findings support the role of the EGF+61 polymorphism as a susceptibility factor for development of gliomas and show its implication on EGF promoter activity.

Hypermethylation and transcriptional downregulation of the CITED4 gene at 1p34.2 in oligodendroglial tumours with allelic losses on 1p and 19q

Deletions of chromosomal arms 1p and 19q are frequent in oligodendroglial tumours and have been associated with sensitivity to radio- and chemotherapy as well as favourable prognosis. By using microarray-based expression profiling, we found that oligodendroglial tumours with 1p and 19q losses showed significantly lower expression of the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 4 gene (CITED4) at 1p34.2 as compared to tumours without 1p and 19q losses. Mutational analysis showed no CITED4 mutations in gliomas. However, 1p and 19q losses as well as low expression of CITED4 transcripts were significantly associated with hypermethylation of the CITED4-associated CpG island. In line with the latter finding, treatment of CITED4 hypermethylated glioma cell lines with 5-aza-2'-deoxycytidine and trichostatine A resulted in a marked increase of the CITED4 transcript levels. Furthermore, CITED4 hypermethylation was significantly associated with longer recurrence-free and overall survival of patients with oligodendroglial tumours. Taken together, our results indicate that CITED4 is epigenetically silenced in the vast majority of oligodendroglial tumours with 1p and 19q deletions and suggest CITED4 hypermethylation as a novel prognostic marker in oligodendroglioma patients.

The presence of necrosis and/or microvascular proliferation does not influence survival of patients with anaplastic oligodendroglial tumours: review of 98 patients

Accurate prognosis for patients with anaplastic oligodendroglial gliomas is increasingly difficult to make. Characterisation of these tumours remains challenging, increasing proportions of oligodendroglial diagnoses in gliomas are reported, and no WHO 2000 grade IV exists for them, so that highly anaplastic tumours can only be grouped with glioblastoma (GBM) or with grade III oligodendroglioma, which have differing clinical behaviour. Longer survival times reported for patients with glioblastoma containing an oligodendroglial element (GBMO) suggest that a grade IV for oligodendroglial tumours might exist. In patients with anaplastic gliomas containing an oligodendroglial element, we explored whether microvascular proliferation (MVP) and necrosis were associated with shorter survival, sufficient to create a grade IV. Biopsies for 98 patients with anaplastic oligodendroglioma, anaplastic oligoastrocytoma or tumours with an oligodendroglial and GBM element, discharged 1998-2004, were identified from databases at three allied neurosurgery units. Pathology reports were reviewed for the presence of MVP and necrosis. Anaplastic oligoastrocytoma and GBMO were combined to measure the effect of an astrocytic element on survival. For anaplastic oligodendroglioma patients, median survival time was 24 months, while for anaplastic oligoastrocytoma or GBMO patients, it was 9 months. Age 60 or over (P=0.006) and astrocytic element (P=0.01) were the only independent predictors of survival. Patients 60 and over with an astrocytic element had 4.6 times the risk of death of patients under 60 with anaplastic oligodendroglioma.A grade IV cannot be created using necrosis or MVP since neither feature predicted survival after adjustment for age and an astrocytic element. However age and an astrocytic element were strong predictors of poorer survival in patients with anaplastic oligodendroglial tumours.

Diagnostic and prognostic significance of a t(1;19)(q10;p10) in patients (pts) with low-grade oligodendroglioma and astrocytoma: NCCTG 94–72–53

1505 Background: Combined deletion of chromosomes 1p and 19q is associated with improved prognosis in pts with anaplastic oligodendroglioma. We recently discovered that the combined deletion is mediated by a chromosome 1;19 translocation: t(1;19)(q10;p10). The prognostic significance of this alteration in pts with low-grade gliomas is not known. Methods: Paraffin-embedded tumor tissue was obtained from 134 pts enrolled in two NCCTG trials for newly-diagnosed low-grade glioma: 86–72–51: a randomized phase III trial of 50.4 Gy vs 64.8 Gy radiation therapy (RT) and 93–72–02: a phase II trial of PCV for 6 cycles followed by RT. Interphase fusion of a CEP1 probe and a BAC contig probe for 19p12 was used to detect the 1;19 translocation. Analysis of 1p and 19q deletions had been previously performed by FISH. Kaplan-Meier distributions of overall survival (OS) and progression-free survival (PFS) for pts whose tumors did or did not exhibit CEP1/19p12 fusion were compared using the Wilcoxon test. Results: Of 134 pts, CEP1/19p12 fusion testing was informative for 92. CEP1/19p12 fusion prevalence was 55% among 42 oligodendrogliomas, 47% among 30 mixed oligoastrocytomas, and 5% among 20 astrocytomas. 91% of gliomas with and 11% without 1p/19q deletion had CEP1/19p12 fusion (p&lt;0.0001, chi-square test). The frequency of the t(1;19) by tumor histology, as well as median and 5-year progression-free and overall survival are provided in the table . Conclusions: Our results strongly suggest that a t(1;19)(q10;p10) mediates the combined deletion of 1p and 19q in human gliomas. Like combined 1p and 19q deletion, the 1;19 translocation is associated with superior progression-free and overall survival in low-grade oligodendroglioma patients. FISH analysis of the t(1;19) will likely be a more sensitive and specific means to assess 1p and 19q status in patients with gliomas. (Supported in part by CA85799, CA108961 and NCCTG grants CA25224 and CA114740) [Table: see text] No significant financial relationships to disclose.

First analysis of EORTC trial 26951, a randomized phase III study of adjuvant PCV chemotherapy in patients with highly anaplastic oligodendroglioma

1503 Background. Anaplastic oligodendroglioma are sensitive to chemotherapy. EORTC 26951 was initiated to investigate whether the addition of 6 cycles PCV chemotherapy after radiotherapy (RT) improves overall survival (OS) and progression free survival (PFS). Methods. Eligibility criteria: histologically confirmed newly diagnosed anaplastic oligodendroglioma (AOD) or anaplastic oligoastrocytoma (AOA) with ≥ 25% oligodendral elements; age between 18–70 years; ECOG Performance Status (PS) 0–2; written informed consent. After stratification for age, institution, extent of resection, ECOG PS, and prior surgery for a low grade oligodendroglioma patients were randomized to either 33 x 1.8 Gy radiotherapy (control arm) or to the same radiotherapy followed by 6 cycles of standard PCV chemotherapy (PCV arm). Primary endpoint was overall survival, with PFS as a secondary endpoint. Results. 368 patients were randomised, 185 to the PCV arm and 183 patients to the control arm. Median follow-up is 4.1 years, 204 patients (55.4%) have died. Treatment groups were well balanced with respect to known prognostic factors. The median number of administered PCV cycles was 3; 35% of patients completed at least 5 cycles. At recurrence, PCV chemotherapy was given to 64% of patients in the control arm vs to 11% in the PCV arm. In addition, 51% of the patients in the PCV arm and 48% of patients in the control arm received other chemotherapy (mostly temozolomide) at recurrence. PFS was significantly increased after adjuvant PCV chemotherapy (table; hazard ratio (HR) 0.69; 95% confidence interval (CI) [0.53;0.88], p = 0.0035). However, no difference in OS was observed (HR 0.88; 95% CI [0.67;1.16]. Conclusion. Adjuvant PCV chemotherapy prolongs PFS from 13 months to 24 months in AOD/AOA, without a statistically significant improvement of OS. Analysis of 1p/19q status is in progress. No significant financial relationships to disclose.

Efficacy and Toxicity of Postoperative Temozolomide Radiochemotherapy in Malignant Glioma

To evaluate the feasibility, safety and efficacy of daily temozolomide concurrent with postoperative radiotherapy in malignant glioma. From 11/1999 to 03/2003, n = 81 patients aged 15-72 years (median 52 years, Karnofsky score 80-100% in 83%) suffering from primary glioblastoma (n = 47), anaplastic astrocytoma (n = 6), anaplastic oligodendroglioma (n = 16), and recurrent glioma (n = 12) were treated. Patients with primary gliomas received a combination of postoperative radiotherapy (60 Gy/1.8- to 2.0-Gy fractions) and daily oral temozolomide (75 mg/m(2)) at all irradiation days (30-33 doses), while recurrent tumors were treated with 45-60 Gy and temozolomide. Initially, 6/81 patients had daily temozolomide doses of 50 mg/m(2). In total, 70/81 patients (86%) completed both radio- and chemotherapy. Grade 1 nausea/vomiting was seen in 28%, grade 2 in 11%, grade 3 in 1%. Antiemetics were applied in 41%. Hematologic toxicities were observed as follows: leukopenia grade 3/4 1%, lymphopenia grade 3/4 46%, thrombopenia grade 3/4 1%. Two patients under dexamethasone suffered herpes encephalitis after one and 16 doses of temozolomide (75 mg/m(2)). Median survival was 15 months for glioblastoma. In oligodendroglioma patients, a 4-year survival rate of 78% was observed. Postoperative radiochemotherapy with 30-33 daily doses of temozolomide (75 mg/m(2)) is safe in patients with malignant glioma. The combined schedule is effective in oligodendroglioma patients and may prolong survival in glioblastoma. Effort should be taken to minimize corticosteroid doses, since both steroids and temozolomide lead to immunosuppression.

Successful treatment of low‐grade oligodendroglial tumors with a chemotherapy regimen of procarbazine, lomustine, and vincristine

Anaplastic oligodendroglioma (OD) tumors, especially those with the combined loss of the short arm of chromosome 1 (1p) and the long arm of chromosome 19 (19q), are sensitive to chemotherapy. Only limited data are available on the role of chemotherapy in low-grade OD. The authors retrospectively studied the outcome of the procarbazine, lomustine, and vincristine (PCV) chemotherapy regimen in a group of 16 patients with newly diagnosed OD and 5 patients with recurrent low-grade OD. Two groups of patients were studied: newly diagnosed patients with large OD and mixed oligoastrocytomas (OA) and patients with recurrent OD and OA after radiotherapy who still showed nonenhancing tumors. Treatment consisted of standard PCV chemotherapy. In the newly diagnosed and responding patients, radiotherapy was withheld until the time of disease recurrence. Responses were assessed by T2-weighted magnetic resonance image (MRI) scans. Loss of chromosome 1p and 19q was assessed using fluorescent in situ hybridization with locus-specific probes. Three of five patients with recurrent tumors responded. Thirteen of the 16 newly diagnosed patients showed evidence of response. The median time to disease progression in this group was >24 months. Only one of these patients experienced disease progression while receiving chemotherapy. Several patients showed a signficant clinical improvement despite only a modest improvement of the tumor on the MRI scans. Even patients without loss of 1p or 19q showed satisfactory responses. No TP53 mutations were found. Newly diagnosed patients with OD tumors, with or without loss of 1p/19q, responded to PCV chemotherapy. Up-front chemotherapy may be indicated especially for patients with large tumors. MRI scans were of limited value for the assessment of response. A Phase III trial should be initiated to compare radiotherapy with chemotherapy.

Frequent promoter hypermethylation and low expression of the MGMT gene in oligodendroglial tumors.

Allelic losses on the chromosome arms 1p and 19q have been associated with favorable response to chemotherapy and good prognosis in anaplastic oligodendroglioma patients, but the molecular mechanisms responsible for this relationship are as yet unknown. The DNA repair enzyme O(6)-methylguanine DNA methyltransferase (MGMT) may cause resistance to DNA-alkylating drugs commonly used in the treatment of anaplastic oligodendrogliomas and other malignant gliomas. We report on the analysis of 52 oligodendroglial tumors for MGMT promoter methylation, as well as mRNA and protein expression. Using sequencing of sodium bisulfite-modified DNA, we determined the methylation status of 25 CpG sites within the MGMT promoter. In 46 of 52 tumors (88%), we detected MGMT promoter hypermethylation as defined by methylation of more than 50% of the sequenced CpG sites. Real-time reverse transcription-PCR showed reduced MGMT mRNA levels relative to non-neoplastic brain tissue in the majority of tumors with hypermethylation. Similarly, immunohistochemical analysis showed either no or only small fractions of MGMT positive tumor cells. MGMT promoter hypermethylation was significantly more frequent and the percentage of methylated CpG sites in the investigated MGMT promoter fragment was significantly higher in tumors with loss of heterozygosity on chromosome arms 1p and 19q as compared to tumors without allelic losses on these chromosomes arms. Taken together, our data suggest that MGMT hypermethylation and low or absent expression are frequent in oligodendroglial tumors and likely contribute to the chemosensitivity of these tumors.

Long-term outcome of oligodendrogliomas.

Favorable prognostic factors for oligodendroglial tumors include age younger than 40 years, low tumor grade, and extent of resection. To assess survival time and prognostic factors of 100 patients with oligodendrogliomas diagnosed between 1995 and 2002. The tumors were rated histologically by the WHO classification as low grade (grade II) or anaplastic (grade III). One hundred patients were categorized into three groups: group A: grade II, group B: secondary grade III (low grade with anaplastic transformation during the follow-up), group C: de novo grade III. All patients were symptomatic at presentation and underwent neurosurgical procedure for histologic diagnosis. Follow-up was performed with clinical assessment, brain MRI, and MIBI scintigraphy. There were 66 men and 34 women (mean age at diagnosis 46.7 years). The most common first symptom was partial epileptic seizure (75%). Fifty-six patients had initial gadolinium enhancement (A: 15.6%; B: 36.8% as grade II, 95% as grade III; C: 90%), generally associated with MIBI hypermetabolism (p < 0.0001). Survival rates at 2, 5, and 10 years were A: 88%, 88%, 85%; B: 79%, 64%, 42%; C: 43%, 16%, 15%. Secondary anaplastic oligodendroglioma patients were younger than patients with de novo anaplastic oligodendrogliomas. Histologic confirmation is mandatory because some low grade oligodendrogliomas had gadolinium enhancement on MRI and some anaplastic did not. Survival time was longer for secondary than for de novo anaplastic oligodendrogliomas without difference in the duration of the malignant phase of the disease.

Immunohistochemical markers for prognosis of oligodendroglial neoplasms.

Despite numerous previous studies, oligodendrogliomas continue to generate considerable controversy in the identification of prognostic factors, including single histopathological patterns, and grade of tumor malignancy. The prognostic significance of various pathological and immunohistochemical factors has been intensively examined but numerous studies have yielded conflicting results. In the present study, biopsy samples of 123 oligodendrogliomas were examined immunohistochemically to evaluate a possible association between expression of various tumor-associated antigens and clinical outcome. Both the progression-free and overall survival times were significantly reduced for high-grade tumors, for Ki-S1 labeling index (LI) > 10%, for p27 LI < 20% and for p18, p53, and vascular endothelial growth factor (VEGF)-positive tumors. For low-grade tumors survival rates were significantly reduced for p27 LI less than 20%, whereas high-grade oligodendrogliomas with Ki-S1 LI greater than 10%, and with p18 positivity revealed significantly shortened survival times. We found no differences in survival times in patients with or without p 14ARF, p21, mdm2, and pRb immunoreactivity. Multivariate analysis revealed that risk of oligodendroglioma progression is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p27 LI < 20%; whereas risk of death is associated with high-grade tumors, with Ki-S1 LI > 10%, and with p18 positivity. CART modeling process identified four final groups of oligodendroglioma patients: (1) thirty-nine patients with low-grade tumors and p27 LI > 20%; (2) twenty patients with low-grade tumors and p27 LI < 20%; (3) thirty-four patients with high-grade tumors and Ki-S1 LI < 10%; and (4) thirty patients with high-grade tumors and Ki-S1 LI >10%. In summary, both the p27 and Ki-S1 scores were found to be the strong predictors of oligodendroglioma outcome together with the WHO tumor grade and they seem to be useful for assessing individual prognosis in routinely processed specimens.

High topoisomerase IIalpha expression associates with high proliferation rate and and poor prognosis in oligodendrogliomas.

The role of molecular markers predicting the prognosis and the selection of patients for further adjuvant therapies is not well established in oligodendroglioma patients. A potential prognostic as well as a therapeutically predictive factor, topoisomerase IIalpha (topoIIalpha), is a molecular target for certain cytotoxic drugs. Its expression has been shown to correlate with the prognosis in a number of different cancers and with the chemosensitivity of cancer cells in vitro. The expression of topoIIalpha was evaluated immunohistochemically in 59 oligodendrogliomas and in 29 mixed gliomas with a predominating oligodendroglioma component by the use of a tissue microarray technique. In the gliomas, the percentage of topoIIalpha immunopositive cells protein expression varied from 0.0 to 49.1% (5.2 +/- 8.3%, mean+/- SD). In oligoastrocytomas, the mean topoIIalpha score was significantly higher in the oligodendroglioma than in the astrocytoma component of the tumour (5.37 +/- 5.58% vs. 1.89 +/- 2.49%, P = 0.018). A significant association was found between the high proportion of topoIIalpha positive cells and high grade of the tumour (P < 0.0001), high tumour proliferation rate (P < 0.0001), p53 overexpression (P = 0.01) and high expression of tumour suppressing retinoblastoma protein (P = 0.023). TopoIIalpha expression was not associated with the age or sex of patient, and the rate of apoptosis. TopoIIalpha expression associated highly significantly with patient prognosis; a significantly higher proportion of patients with low rather than with high topoIIalpha score was alive at the end of the 5-year follow-up (P = 0.03). Cox analysis was used to demonstrate that topoIIalpha had an independent prognostic value for survival (P = 0.034). In conclusion, high topoIIalpha expression characterizes oligodendrogliomas and oligoastrocytomas which are poorly differentiated, have high proliferation rate, and has prognostic value for overall survival of these patients. Therefore, topoIIalpha may be a useful marker for better targeted selection of poor prognosis oligodendroglioma patients for adjuvant therapy.

Alterations of chromosome arms 1p and 19q as predictors of survival in oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas.

A recent report suggests that alterations of chromosome arms 1p and 19q are associated with chemotherapeutic response and overall survival in anaplastic oligodendroglioma patients treated with procarbazine, lomustine, and vincristine chemotherapy. We set out to further clarify the diagnostic and prognostic implications of these alterations in a broader set of diffuse gliomas, including astrocytic neoplasms and low-grade oligodendrogliomas. Fluorescence in situ hybridization (FISH) signals from DNA probes mapping to 1p and 19q common deletion regions were enumerated in 162 diffuse gliomas (79 astrocytomas, 52 oligodendrogliomas, and 31 mixed oligoastrocytomas), collected as part of an ongoing prospective investigation of CNS tumors. The oligodendroglial phenotype was highly associated with loss of 1p (P =.0002), loss of 19q (P <.0001), and combined loss of 1p and 19q (P <.0001). Combined loss of 1p and 19q was identified as a univariate predictor of prolonged overall survival among patients with pure oligodendroglioma (log-rank, P =.03) and remained a significant predictor after adjusting for the effects of patient age and tumor grade (P <.01). This favorable association was not evident in patients with astrocytoma or mixed oligoastrocytoma. Combined loss of 1p and 19q is a statistically significant predictor of prolonged survival in patients with pure oligodendroglioma, independent of tumor grade. Given the lack of this association in patients with astrocytic neoplasms and the previously demonstrated chemosensitivity of oligodendrogliomas, a combined approach of histologic and genotypic assessment could potentially improve existing strategies for patient stratification and management.