Correlations Between O6-Methylguanine DNA Methyltransferase Promoter Methylation Status, 1p and 19q Deletions, and Response to Temozolomide in Anaplastic and Recurrent Oligodendroglioma: A Prospective GICNO Study

Diagnostic and prognostic markers in gliomas

PURPOSE OF REVIEW

This review summarizes recent studies on diagnostic and prognostic markers in gliomas such as the BRAF fusion gene in pilocytic astrocytomas and 1p/19q codeletion, O-6-methylguanine-DNA methyltransferase status and isocitrate dehydrogenase 1 (IDH1)/IDH2 mutations in diffuse gliomas.

RECENT FINDINGS

In pilocytic astrocytomas, the BRAF fusion gene has been recently identified as a specific and frequent event leading to potentially targetable mitogen-activated protein kinase pathway activation. In grade II/III gliomas and in glioblastomas, chromosome 1p/19q codeletion and O-6-methylguanine-DNA methyltransferase status remain the most important prognostic and predictive markers. Recently identified mutations in IDH1/IDH2, however, are specific for diffuse gliomas, occur frequently in grade II/III gliomas and are of prognostic value in grade III gliomas, as well in glioblastomas in which they characterize secondary glioblastomas.

SUMMARY

Extensive molecular studies have enabled the discovery of new diagnostic and prognostic markers that are refining the histomolecular classification of gliomas.

Intra-arterial chemotherapy with osmotic blood-brain barrier disruption for aggressive oligodendroglial tumors: results of a phase I study

OBJECTIVE

Refractory anaplastic oligodendroglioma and oligoastrocytoma tumors are challenging to treat. This trial primarily evaluated toxicity and estimated the maximum tolerated dose of intra-arterial (IA) melphalan, IA carboplatin, and intravenous (IV) etoposide phosphate in conjunction with blood-brain barrier disruption in these tumors. The secondary measure was efficacy.

METHODS

Thirteen patients with temozolomide-refractory anaplastic oligodendroglioma (11 patients) or oligoastrocytoma (2 patients) underwent blood-brain barrier disruption with carboplatin (IA, 200 mg/m(2)/d), etoposide phosphate (IV, 200 mg/m(2)/d), and melphalan (IA, dose escalation) every 4 weeks, for up to 1 year. Patients underwent melphalan dose escalation (4, 8, 12, 16, and 20 mg/m(2)/d) until the maximum tolerated dose (1 level below that producing grade 4 toxicity) was determined. Toxicity and efficacy were assessed.

RESULTS

Two of 4 patients receiving IA melphalan at 8 mg/m(2)/d developed grade 4 thrombocytopenia; thus, the melphalan maximum tolerated dose was 4 mg/m/d. Adverse events included asymptomatic subintimal tear (1 patient) and grade 4 thrombocytopenia (3 patients). Two patients demonstrated complete response, 3 had partial responses, 5 demonstrated stable disease, and 3 progressed. Median overall progression-free survival was 11 months. Patients with complete or partial response demonstrated deletion of chromosomes 1p and 19q. In the 5 patients with stable disease, 2 demonstrated 1p and 19q deletion, and 3 demonstrated 19q deletion only.

CONCLUSION

In patients with anaplastic oligodendroglioma or oligoastrocytoma tumors in whom temozolomide treatment has failed, osmotic blood-brain barrier disruption with IA carboplatin, IV etoposide phosphate, and IA melphalan (4 mg/m(2)/d for 2 days) shows acceptable toxicity and encouraging efficacy, especially in patients demonstrating 1p and/or 19q deletion.

MGMT promoter methylation in malignant gliomas: ready for personalized medicine?

The DNA repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT) antagonizes the genotoxic effects of alkylating agents. MGMT promoter methylation is the key mechanism of MGMT gene silencing and predicts a favorable outcome in patients with glioblastoma who are exposed to alkylating agent chemotherapy. This biomarker is on the verge of entering clinical decision-making and is currently used to stratify or even select glioblastoma patients for clinical trials. In other subtypes of glioma, such as anaplastic gliomas, the relevance of MGMT promoter methylation might extend beyond the prediction of chemosensitivity, and could reflect a distinct molecular profile. Here, we review the most commonly used assays for evaluation of MGMT status, outline the prerequisites for standardized tests, and evaluate reasons for difficulties in reproducibility. We critically discuss the prognostic and predictive value of MGMT silencing, reviewing trials in which patients with different types of glioma were treated with various chemotherapy schedules, either up-front or at recurrence. Standardization of MGMT testing requires comparison of different technologies across laboratories and prospectively validated cut-off values for prognostic or predictive effects. Moreover, future clinical trials will need to determine, for each subtype of glioma, the degree to which MGMT promoter methylation is predictive or prognostic, and whether testing should become routine clinical practice.

MGMT promoter methylation is prognostic but not predictive for outcome to adjuvant PCV chemotherapy in anaplastic oligodendroglial tumors: a report from EORTC Brain Tumor Group Study 26951

PURPOSE

O6-methylguanine-methyltransferase (MGMT) promoter methylation has been shown to predict survival of patients with glioblastomas if temozolomide is added to radiotherapy (RT). It is unknown if MGMT promoter methylation is also predictive to outcome to RT followed by adjuvant procarbazine, lomustine, and vincristine (PCV) chemotherapy in patients with anaplastic oligodendroglial tumors (AOT).

PATIENTS AND METHODS

In the European Organisation for the Research and Treatment of Cancer study 26951, 368 patients with AOT were randomly assigned to either RT alone or to RT followed by adjuvant PCV. From 165 patients of this study, formalin-fixed, paraffin-embedded tumor tissue was available for MGMT promoter methylation analysis. This was investigated with methylation specific multiplex ligation-dependent probe amplification.

RESULTS

In 152 cases, an MGMT result was obtained, in 121 (80%) cases MGMT promoter methylation was observed. Methylation strongly correlated with combined loss of chromosome 1p and 19q loss (P = .00043). In multivariate analysis, MGMT promoter methylation, 1p/19q codeletion, tumor necrosis, and extent of resection were independent prognostic factors. The prognostic significance of MGMT promoter methylation was equally strong in the RT arm and the RT/PCV arm for both progression-free survival and overall survival. In tumors diagnosed at central pathology review as glioblastoma, no prognostic effect of MGMT promoter methylation was observed.

CONCLUSION

In this study, on patients with AOT MGMT promoter methylation was of prognostic significance and did not have predictive significance for outcome to adjuvant PCV chemotherapy. The biologic effect of MGMT promoter methylation or pathogenetic features associated with MGMT promoter methylation may be different for AOT compared with glioblastoma.

Polysomy for chromosomes 1 and 19 predicts earlier recurrence in anaplastic oligodendrogliomas with concurrent 1p/19q loss

PURPOSE

Loss of chromosome arms 1p and 19q is a molecular feature of oligodendroglial tumors characterized by responsiveness to chemotherapy and a favorable prognosis. The purpose of this study was to evaluate the prognostic significance of polysomy of chromosomes 1 and 19 in the setting of 1p/19q codeletion.

EXPERIMENTAL DESIGN

We analyzed 64 anaplastic oligodendrogliomas with 1p/19q loss or maintenance diagnosed at Massachusetts General Hospital and Brigham and Women's Hospital from 1996 to 2005; fluorescence in situ hybridization for 1p/19q and Ki-67 immunohistochemistry was done. Polysomy was defined as more than two 1q and 19p signals in >30% of the cells with concurrent 1p/19q deletion. Tumors were divided into groups based on their 1p/19q status and compared for progression-free survival, overall survival, and 5-year survival probabilities.

RESULTS

Forty-six tumors (72%) in our cohort had 1p/19q loss and 18 (28%) had 1p/19q maintenance. Of those with loss, 19 (41%) had concurrent polysomy and 27 (59%) lacked polysomy. In agreement with previous studies, the group of anaplastic oligodendrogliomas with 1p/19q loss had significantly better progression-free survival and overall survival than anaplastic oligodendrogliomas with 1p/19q maintenance (P = 0.0009 and P < 0.0003, respectively). Among anaplastic oligodendrogliomas with 1p/19q loss, those with polysomy showed shorter progression-free survival than those with 1p/19q loss without polysomy (P = 0.0048). Overall survival was similar in tumors with and without polysomy. The Ki-67 labeling index was not associated with polysomy and did not have prognostic significance.

CONCLUSION

The presence of polysomy in anaplastic oligodendrogliomas with deletion of 1p/19q is a marker of earlier recurrence.

Utility of gene promoter methylation in prediction of response to platinum-based chemotherapy in epithelial ovarian cancer (EOC)

The aim was to determine whether promoter methylation of BRCA1, MGMT, MLH1, RASSF1A, and p16 genes could predict response to platinum-based chemotherapy. Thirty-five subjects with epithelial ovarian cancer (EOC) treated by platinum-based chemotherapy were recruited. Methylation-specific polymerase chain reaction was carried out and the methylation index (MI) was also derived. Response to platinum-based chemotherapy was documented clinically, radiologically, and by serial CA125 levels. Methylated BRCA1 (p = .037) and a higher MI (p = .045) were associated with primary chemosensitivity. A better outcome was predicted by a higher MI (p = .032). In EOC, BRCA1 gene promoter methylation is useful in the prediction of response to chemotherapy.

Prognostic and predictive value of p53 in low MGMT expressing glioblastoma treated with surgery, radiation and adjuvant temozolomide chemotherapy

OBJECTIVE

To assess the prognostic and predictive significance of p53 protein expression in low O6-methylguanine-DNA methyltransferase (MGMT) expressing glioblastoma multiform (GBM) treated with combined therapy.

METHODS

The authors reviewed the clinical outcomes of 46 low MGMT expressing GBM patients who had undergone surgery, conventional local radiotherapy and temozolomide chemotherapy. Correlation between p53 expression level and clinical outcomes were analysed with univariate and multivariate Cox model.

RESULTS

Patients with low p53 expression had a significantly improved progression free survival (PFS) (p=0.015) and overall survival (OS) (p=0.047) compared to those with high expression. On both univariate and multivariate analyses, low p53 expression persisted as a significant independent favorable prognostic factor for PFS (p=0.017). Pre-operative Karnofsky performance status score (p=0.029), tumor resection extent (p=0.045) and p53 expression level (p=0.038) were significant independent prognostic factors for OS.

CONCLUSION

In these low MGMT expressing GBM patients with combined treatment, low p53 expression was a significant independent favorable prognostic factor for both PFS and OS. In addition to MGMT, p53 may be another stratification variable in the future therapeutic trials.

Allelic status of 1p and 19q in oligodendrogliomas and glioblastomas: multiplex ligation-dependent probe amplification versus loss of heterozygosity

Identification of the 1p/19q allelic status in gliomas, primarily those with a major oligodendroglial component, has become an excellent molecular complement to tumor histology in order to identify those cases sensitive to chemotherapy. In addition to loss of heterozygosity (LOH), fluorescence in situ hybridization (FISH), or comparative genomic hybridization (CGH), multiplex ligation-dependent probe amplification (MLPA) has been shown to be an alternative methodology to identify deletions of those chromosome arms. We used MLPA to explore the 1p and 19q allelic constitution in a series of 76 gliomas: 41 tumors with a major oligodendroglial component, 34 glioblastomas, and one low-grade astrocytoma. We compared the MLPA findings of the oligodendroglial cases with those previously obtained using LOH in the same samples. Thirty-eight of 41 oligodendrogliomas displayed identical findings by both LOH and MLPA, and losses at either 1p and/or 19q were identified in 12 of 35 (34%) astrocytic tumors. These findings agree with data previously reported comparing MLPA versus FISH or CGH in gliomas and suggest that MLPA can be used in the identification of the 1p/19q allelic deletions on these brain neoplasms.

Diffuse leptomeningeal glioneuronal tumors: a new entity?

The peculiar radiological and pathological findings of four pediatric cases admitted to the University Hospital of Padua between 1990 and 2007 are described. In all cases, the contrast-enhanced head and spine magnetic resonance images revealed thickened and abnormally enhancing subarachnoid spaces particularly at the level of basal cisterns and interhemispheric fissure. Furthermore, small cystic lesions scattered throughout the brain and mainly in the cerebellum were also visible. All patients were missing a well-defined intraparenchymal mass, although during the follow-up a small intramedullary lesion appeared within the cervical spine in two and subsequently in the frontal horn of the left lateral ventricle in one of those. All patients presented an indolent long-term follow-up. Histologically, the tumors were composed by a monotonous population of cells arranged in straight lines or in small lobules. The cells were characterized by round to oval nuclei with finely granular dispersed chromatin, inconspicuous nucleoli with oligodendrocyte-like features. The morphological and immunohistochemical findings suggested in all cases a "glioneuronal commitment" of the tumors. Because of the unique similar clinical and neuroradiological characteristics, we propose this small series of tumors as a new possible distinct pathological and clinical entity.

O6-methylguanine DNA methyltransferase deficiency and response to temozolomide-based therapy in patients with neuroendocrine tumors

PURPOSE

Recent studies suggest that temozolomide has activity in neuroendocrine tumors. Low levels of the DNA repair enzyme, O(6)-methylguanine DNA methyltransferase (MGMT), are associated with sensitivity to temozolomide in other tumor types. We evaluated the prevalence of MGMT deficiency in neuroendocrine tumors and correlated MGMT deficiency with treatment response to temozolomide-based regimens.

EXPERIMENTAL DESIGN

The prevalence of MGMT deficiency, measured by immunohistochemistry, was assessed in 97 archival neuroendocrine tumor specimens. Rates of treatment response and survival were next evaluated in a cohort of 101 consecutive neuroendocrine tumor patients who had received treatment with a temozolomide-based regimen at one of three institutions. MGMT expression was directly correlated with treatment response in 21 patients who had available tumor tissue and response data.

RESULTS

In archival specimens, MGMT deficiency was observed in 19 of 37 (51%) pancreatic neuroendocrine tumors and 0 of 60 (0%) carcinoid tumors (P < 0.0001). In the clinical cohort, 18 of 53 (34%) patients with pancreatic neuroendocrine tumors but only 1 of 44 (2%) patients with carcinoid tumors (P < 0.001) experienced a partial or complete response to temozolomide-based therapy. Among 21 patients with evaluable tumor tissue who had also received treatment with temozolomide, 4 of 5 patients with MGMT-deficient tumors (all pancreatic neuroendocrine tumors) and 0 of 16 patients with tumors showing intact MGMT expression responded to treatment (P = 0.001).

CONCLUSIONS

MGMT deficiency, measured by immunohistochemistry, is more common in pancreatic neuroendocrine tumors than in carcinoid tumors as is treatment response to temozolomide-based therapy. Absence of MGMT may explain the sensitivity of some pancreatic neuroendocrine tumors to treatment.

The role of chemotherapy for pure and mixed anaplastic oligodendroglial tumors

Pure and mixed anaplastic oligodendrogliomas (AO/mixed-AOs) remain terminal primary brain tumors, without a defined optimal initial therapy, and without sufficiently active and tolerable therapies at recurrence/progression (R/P). Very heterogeneous international therapy recommendations remain. Historical advances have resulted in only modest improvements in outcome. AO/mixed-AOs with 1p/19q co-deletion are prognostically favorable, regardless of therapy, and must be identified as early as possible. Following resection, outcome data on initial therapy with radiation (RT) remain the most mature, although controversies regarding its true toxicities and optimal timing continue. Recently, the landmark RTOG 9402 and EORTC 26951 trials showed that the addition of Procarbazine, CCNU, Vincristine chemotherapy to RT, at anytime during initial therapy, prolongs progression-free survival, but not survival, and not without moderate toxicity. Despite a lack of definitive evidence, this strategy has commonly been extrapolated to Temozolomide. Chemo-sensitivity of AO/mixed-AOs provides the rationale for the chemotherapy-only strategies being explored. In the setting of recurrence/progression (R/P), chemotherapy, small molecule (targeted), biologic, and other strategies have been relatively disappointing, toxic, and cumbersome. Partly secondary to biases regarding the relative toxicities of tumor burden vs. treatment effect, therapy remains highly individualized. Future international research must prospectively evaluate health-related quality of life, toxicity, and molecular genetic markers.

Molecular profiling of oligodendrogliomas: impact on prognosis, treatment, and future directions

Oligodendrogliomas account for a small subset of all gliomas, but they often are more sensitive to treatment than other glioma subtypes. In addition, oligodendrogliomas are the first central nervous system neoplasm for which a specific molecular abnormality, allelic loss of 1p/19q (1p/19q loss), correlates with patient outcome in large-scale prospective clinical trials. However, the incorporation of 1p/19q status into clinical practice remains controversial. Other molecular alterations found in oligodendrogliomas include hypermethylation of the promoter for the MGMT gene, TP53 mutations, EGFR and platelet-derived growth factor/PDGFR alterations, and 9p and 10q loss.

Complete Radiologic Response in an Anaplastic Oligodendroglioma Treated with Temozolomide and Bevacizumab

In this case report, we describe a rare case of a 32-year-old man who presented a highly aggressive, fast growing anaplastic oligodendroglioma five years after being treated with whole brain radiotherapy for a CNS recurrence of a lymphoblastic lymphoma. Initially, the patient was submitted to a surgical intervention and partial tumor resection, which allowed us to establish the pathologic diagnosis and the presence of a 1p deletion. Shortly after the operation the tumor grew back, exerting important mass effect. Since no radiation therapy or surgery could be used and the patient faced a critical condition, chemotherapy was started with a combination of temozolomide and bevacizumab. Immediately after the first cycle a marked clinical and radiological improvement was documented.

Recurrence pattern after temozolomide concomitant with and adjuvant to radiotherapy in newly diagnosed patients with glioblastoma: correlation With MGMT promoter methylation status

PURPOSE

The aim of the present study was to evaluate factors predicting the recurrence pattern after the administration of temozolomide (TMZ), initially concurrent with radiotherapy (RT) and subsequently as maintenance therapy, which has become standard treatment for patients with newly diagnosed glioblastoma (GBM).

PATIENTS AND METHODS

Ninety-five patients with newly diagnosed GBM were treated with RT plus TMZ (75 mg/m(2)/d) followed by maintenance TMZ cycles (150 to 200 mg/m(2) for 5 days every 28 days). Assessable MGMT methylation status and magnetic resonance imaging follow-up were mandatory in all cases.

RESULTS

After a median follow-up of 18.9 months (range, 6.6 to 44.8 months), 79 patients (83%) had recurrence: inside the RT field in 57 patients (72.2%), outside in 17 patients (21.5%), and at RT margin in five patients (6.3%). MGMT status was correlated with the site of recurrence, which occurred inside, or at the margin of, the RT field in 51 patients (85%) with MGMT unmethylated status and in 11 patients (57.9%) with MGMT methylated status (P = .01). Recurrences outside the RT field occurred after a longer time interval than those inside the RT field (14.9 v 9.2 months, P = .02).

CONCLUSION

After the administration of TMZ concomitant with and adjuvant to RT in patients with GBM, the pattern of, and time to, recurrence are strictly correlated with MGMT methylation status.

Oligodendrogliomas: molecular biology and treatment

Oligodendroglial tumors continue to receive much attention because of their relative sensitivity to chemotherapy. The histological diagnosis of oligodendroglial tumors is subject to considerable interobserver variation. The revised 2007 World Health Organization classification of brain tumors no longer accepts the diagnosis "mixed anaplastic oligoastrocytoma" if necrosis is present; these tumors should be considered glioblastomas (perhaps with oligodendroglial features). The 1p/19q codeletion that is associated with sensitivity to chemotherapy is mediated by an unbalanced translocation of 19p to 1q. Randomized studies have shown that patients with 1p/19q codeleted tumors also have a better outcome with radiotherapy. Histologically more atypical tumors are less likely to have this 1p/19q codeletion; here, other alterations usually associated with astrocytic tumors are often found. Some patients with tumors with classic histological features but no 1p/19q codeletion still have a very favorable prognosis. Currently, the best approach for newly diagnosed anaplastic oligodendroglial tumors is unclear. Early adjuvant chemotherapy does not provide a better outcome than chemotherapy at the time of progression. The value of combined chemoirradiation with temozolomide has not been proven in these tumors, and could at least theoretically be associated with greater neurotoxicity. Tumors with 1p and 19q loss can also be managed with early chemotherapy, while deferring radiotherapy to the time of further progression. The presently available second-line chemotherapy results are modest, and better salvage treatments are necessary. The molecular explanation for the greater sensitivity of 1p/19q codeleted tumors is still unclear, and this could, in part, be explained by more frequent MGMT promoter gene methylation.

Molecular pathology of oligodendroglial tumors

The term oligodendroglioma was created by Bailey, Cushing, and Bucy based on the observation that these tumors share morphological similarities with oligodendrocytes (Bailey and Cushing 1926; Bailey and Bucy 1929). However, a convincing link between oligodendrocytes and oligodendrogliomas still needs to be shown. Oligoastrocytomas or mixed gliomas are histologically defined by the presence of oligodendroglial and astrocytic components. According to the WHO classification of brain tumors, oligodendroglial tumors are separated into oligodendrogliomas WHO grade II (OII), anaplastic oligodendrogliomas WHO grade III (OIII), oligoastrocytomas WHO grade II (OAII), anaplastic oligoastrocytomas WHO grade III (OAIII), and glioblastomas with oligodendroglioma component WHO grade IV (GBMo) (Louis et al. 2007).The perception of oligodendroglial tumors has changed in recent years. The diagnosis of oligodendroglioma or oligoastrocytomas is made much more frequently than 10 years ago. Treatment modalities have been advanced and novel concepts regarding the origin of oligodendroglial tumors have been developed. This review focuses on recent developments with impact on the diagnosis and understanding of molecular mechanisms in oligodendroglial tumors.

Epigenetic markers in human gliomas: prospects for therapeutic intervention

Gliomas represent the most common CNS cancers in adults. Prognosis for patients harboring malignant gliomas is particularly dismal and, despite current treatment strategies comprising surgery, radiotherapy and chemotherapy, the median survival time after diagnosis is still in the range of just 12 months. In recent years, there has been an increased effort to identify tumor biomarkers that can be used as diagnostic tools, or markers for predicting therapeutic response and prognosis. Investigation of genetic changes has identified several such markers that have shown some success in predicting the most effective therapy. In recent years, however, it has become apparent that the biology of many cancers of the CNS is determined not only by their genetic profile but also their epigenetic profile. Epigenetic biomarkers show great potential in effectively predicting patient prognosis and response to therapy. The eventual application of epigenetic profiling of tumors may help to indicate the most effective tailored therapy for individual patients.

Predictive factors for overall and progression-free survival, and dissemination in oligodendroglial tumors

The pattern of recurrence and predictive factors for tumor progression, dissemination and survival in oligodendroglial tumors were investigated. 56 consecutive patients with oligodendroglial tumors were retrospectively analyzed to determine the predictive significance of various factors, including World Health Organization grade, loss of chromosomes 1p and 19q, and immunohistochemical features of TP53, O(6)-methylguanine-deoxyribonucleic-acid-methyltransferase, CD44H, nestin, and Ki-67. Eleven patients developed dissemination, and had significantly shorter post-progression survival compared to ten patients with local recurrence. Univariate analysis showed that retention of chromosome 1p or 19q, Ki-67 labeling index > or = 25%, diffuse expression of nestin, and p53 labeling index > or = 10% were unfavorable factors for overall, progression-free, and dissemination-free survival. Multivariate analysis showed that Ki-67 labeling index > or = 25% and diffuse expression of nestin were significant for dissemination-free survival. In conclusion, post-progression survival shows significant differences between patients with local and disseminated recurrence. Ki-67 labeling index and nestin expression pattern are useful markers to predict dissemination.

[Radiation therapy for glial tumors: technical aspects and clinical indications]

Radiotherapy of glial tumors is rapidly evolving with the recent technical and therapeutic progress. About technical aspects, progress in technical imaging and development of non-coplanar conformal and IMRT techniques provide new possibilities for sparing healthy tissue while increasing dose in tumoral volume. Furthermore, functional and molecular imaging are helpful for delineation and for prediction of relapse. Even modest, the actual improvement of survival with radiochemotherapy leads now to new and important developments for clinical research according to clinical data (age, general status), biological data (MGMT promotor methylation and cytogenetic modifications) and technical data (quality of surgery and radiotherapy). Understanding of molecular mechanisms allows for rational targeting or specific pathways of repair, signaling angiogenesis associated with surgery and radiotherapy in a multidisciplinary approach.

Validation of real-time methylation-specific PCR to determine O6-methylguanine-DNA methyltransferase gene promoter methylation in glioma

Epigenetic silencing of the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) by promoter methylation predicts successful alkylating agent therapy, such as with temozolomide, in glioblastoma patients. Stratified therapy assignment of patients in prospective clinical trials according to tumor MGMT status requires a standardized diagnostic test, suitable for high-throughput analysis of small amounts of formalin-fixed, paraffin-embedded tumor tissue. A direct, real-time methylation-specific PCR (MSP) assay was developed to determine methylation status of the MGMT gene promoter. Assay specificity was obtained by selective amplification of methylated DNA sequences of sodium bisulfite-modified DNA. The copy number of the methylated MGMT promoter, normalized to the beta-actin gene, provides a quantitative test result. We analyzed 134 clinical glioma samples, comparing the new test with the previously validated nested gel-based MSP assay, which yields a binary readout. A cut-off value for the MGMT methylation status was suggested by fitting a bimodal normal mixture model to the real-time results, supporting the hypothesis that there are two distinct populations within the test samples. Comparison of the tests showed high concordance of the results (82/91 [90%]; Cohen's kappa = 0.80; 95% confidence interval, 0.82-0.95). The direct, real-time MSP assay was highly reproducible (Pearson correlation 0.996) and showed valid test results for 93% (125/134) of samples compared with 75% (94/125) for the nested, gel-based MSP assay. This high-throughput test provides an important pharmacogenomic tool for individualized management of alkylating agent chemotherapy.

[Diagnostic and prognostic values of 1p and 19q deletions in adult gliomas: critical review of the literature and implications in daily clinical practice]

Losses of chromosomes 1p and 19q are deemed correlated with diagnosis of oligodendroglioma, higher chemosensitivity and better prognosis. We reviewed the literature to evaluate the usefulness of these correlations in daily clinical practice. The rates of deletions relative to histology (WHO classifications) were extracted from 33 studies, including 2666 patients. The 1p deletions and 1p19q codeletion mean rates were respectively 65.4 and 63.3% in oligodendrogliomas, 28.7 and 21.6% in oligoastrocytomas, 13.2 and 7.5% in astrocytomas, 11.6 and 2.9% in glioblastomas. The presence of 1p deletion and 1p19q codeletion were strongly correlated with the histological diagnosis corresponding to oligodendroglioma. Calculation of specificity, sensitivity, predictive positive values and false negative rates suggests that presence of deletion 1p or codeletion represents a strong argument in favor of the diagnosis of oligodendroglioma. However, considering the high false negative rate, absence of such deletions does not rule out the diagnosis. In grade 3 oligodendroglial tumors, the probability of responding to chemotherapy, and the duration of response, were higher when codeletions were present. This suggests that, in these tumors, the presence of codeletion is a strong argument in favor of adjuvant chemotherapy. However, chemotherapy should not be systematically excluded when codeletions are absent, as the chances of response are about 33% in this situation. Data concerning low-grade gliomas were more controversial. Oligodendroglial tumors with 1p deletion or 1p19q codeletion seemed to have a better prognosis, as five-year survival rates were 50% higher than in tumors without deletion. This might be explained by the correlation between 1p deletion and other identified prognosis factors: (1) higher chemosensitivity, (2) tumor location more frequently in the frontal lobe, leading to better resection and lower risk of neurological deficit, (3) slower growth rate, (4) higher risk of epilepsy, leading to an early detection.

MGMTPromoter Methylation Status Can Predict the Incidence and Outcome of Pseudoprogression After Concomitant Radiochemotherapy in Newly Diagnosed Glioblastoma Patients

Purpose

Standard therapy for glioblastoma (GBM) is temozolomide (TMZ) administration, initially concurrent with radiotherapy (RT), and subsequently as maintenance therapy. The radiologic images obtained in this setting can be difficult to interpret since they may show radiation-induced pseudoprogression (psPD) rather than disease progression.

Methods

Patients with histologically confirmed GBM underwent radiotherapy plus continuous daily temozolomide (75 mg/m2/d), followed by 12 maintenance temozolomide cycles (150 to 200 mg/m2for 5 days every 28 days) if magnetic resonance imaging (MRI) showed no enhancement suggesting a tumor; otherwise, chemotherapy was delivered until complete response or unequivocal progression. The first MRI scan was performed 1 month after completing combined chemoradiotherapy.

Results

In 103 patients (mean age, 52 years [range 20 to 73 years]), total resection, subtotal resection, and biopsy were obtained in 51, 51, and 1 cases, respectively. MGMT promoter was methylated in 36 patients (35%) and unmethylated in 67 patients (65%). Lesion enlargement, evidenced at the first MRI scan in 50 of 103 patients, was subsequently classified as psPD in 32 patients and early disease progression in 18 patients. PsPD was recorded in 21 (91%) of 23 methylated MGMT promoter and 11 (41%) of 27 unmethylated MGMT promoter (P = .0002) patients. MGMT status (P = .001) and psPD detection (P = .045) significantly influenced survival.

Conclusion

PsPD has a clinical impact on chemotherapy-treated GBM, as it may express the glioma killing effects of treatment and is significantly correlated with MGMT status. Improvement in the early recognition of psPD patterns and knowledge of mechanisms underlying this phenomenon are crucial to eliminating biases in evaluating the results of clinical trials and guaranteeing effective treatment.

Predictive and prognostic markers in neuro-oncology

Over the past few years molecular assays have been introduced to aid in typing and grading of gliomas. This is the result of improved understanding of these tumors at the molecular level. In particular, the presence or absence of combined 1p/19 loss in oligodendroglial tumors, epidermal growth factor receptor amplification, epidermal growth factor receptor vIII mutations in grade III tumors and glioblastoma multiforme, and MGMT promoter gene methylation in glioblastoma multiforme are now being used to tailor treatment decisions in patients. However, the application of these tests is far from straightforward, and certain standards are required before any test can be introduced in the daily management of patients. Some of these requirements concern inter- and intratest variability, including whether a test gives the same results if repeated in the same or in another laboratory or when different methodologies are used (e.g. loss of heterozygosity vs fluorescence in situ hybridization and a polymerase chain reaction-based test vs immunohistochemistry). The sensitivity and specificity of a test (or negative and positive predictive value) indicate the likelihood that the test results are positive if the disease is present and the likelihood that the disease is present if the test results are positive. Studies on these test characteristics usually require the presence of a gold standard to which new tests should be compared. Last but not least there is the question of what added value the test has; this criterion determines the clinical usefulness of the assay and why some recently introduced molecular assays need to be scrutinized.

Molecular targeted therapies and chemotherapy in malignant gliomas

PURPOSE OF REVIEW

To review current developments in the field of chemotherapy and targeted treatment of high-grade glioma.

RECENT FINDINGS

Two independent large phase III trials on adjuvant procarbazine, lomustine and vincristine chemotherapy in anaplastic oligodendroglial tumors have shown this improves progression-free survival, but not overall survival, regardless of 1p/19q status. If given sequentially, the timing of procarbazine, lomustine and vincristine chemotherapy has no clear effect on the survival of anaplastic oligodendroglioma. Virtually none of the many new targeted agents directed against pathways that are upregulated in high-grade gliomas has shown significant clinical activity as single agent in phase II studies. The exception are trials with the vascular endothelial growth factor signaling system inhibiting agents bevacizumab and AZD2171 (cediranib) that showed high response rates (which might be due to vessel normalization similar to the effects of steroid treatment) and promising 6-month progression-free survival rates in glioblastoma multiforme.

SUMMARY

Further research to define the role of vascular endothelial growth factor inhibition in the management is indicated. For the many other targeted agents, a critical review of the pathological role of their targets in glioblastoma multiforme is required, especially if combination regimens are investigated. The role of combined chemo-irradiation for non-glioblastoma multiforme high-grade glioma remains to be identified.

Molecular genetic markers as predictors of response to chemotherapy in gliomas

PURPOSE OF REVIEW

This review summarizes recent studies on applications of molecular markers such as chromosome 1p/19q codeletion and MGMT status in the treatment of glioma.

RECENT FINDINGS

Prospective trials confirmed that 1p/19q codeletion represents a strong and independent favourable prognostic factor in anaplastic oligodendroglial tumours. Other retrospective studies have suggested that 1p/19q loss is also predictive of chemosensitivity to alkylating agents (nitrosoureas and temozolomide) in low-grade gliomas. Recent reports have provided evidence that 1p and 19q deletions are mediated by unbalanced translocation. The targeted genes remain to be identified, however. Promoter methylation of MGMT gene silencing has been shown to predict benefit from chemotherapy in glioblastoma. MGMT promoter methylation and low expression of MGMT-encoded protein are frequently observed in low-grade gliomas and anaplastic oligodendroglial tumours. In such tumours, however, preliminary studies have yielded contradictory results on the predictive value of MGMT status regarding objective response to chemotherapy and correlation with 1p/19q deletion.

SUMMARY

There is mounting evidence that 1p/19q deletion and MGMT inactivation are relevant prognostic markers and predictors of chemosensitivity in gliomas. Although such markers remain to be formally validated by ongoing and planned prospective trials, it is likely that they will soon become essential for optimizing treatment decisions.

Phase 2 study of temozolomide in children and adolescents with recurrent central nervous system tumors: a report from the Children's Oncology Group

BACKGROUND

Effective chemotherapy is lacking for most types of central nervous system (CNS) tumors in children. Temozolomide, an agent with activity against adult brain tumors, was investigated in children and adolescents with recurrent CNS tumors.

METHODS

Temozolomide was administered orally as monthly 5-day courses at doses of 200 mg/m(2)/d (patients with no prior craniospinal irradiation [CSI]) or 180 mg/m(2)/d (prior CSI). Patients with a complete (CR) or partial (PR) response or stable disease (SD) could continue temozolomide for up to 12 cycles.

RESULTS

The cohort comprised 122 patients, including 113 with CNS tumors. Median age was 11 years (range, 1-23 years). Among 104 evaluable patients with CNS tumors, 5 PRs and 1 CR were observed. PRs occurred in 1 of 23 evaluable patients with high-grade astrocytoma, 1 of 21 with low-grade astrocytoma, and 3 of 25 with medulloblastoma/primitive neuroectodermal tumor (PNET). The CR occurred in an additional patient with medulloblastoma/PNET. No responses were observed in patients with ependymoma, brain-stem glioma, or other CNS tumors. Notably, 41% of patients with low-grade astrocytoma had SD through 12 courses. The most frequent toxicities were grade 3 or 4 neutropenia (19%) and thrombocytopenia (25%); nonhematologic toxicity was infrequent.

CONCLUSIONS

Although overall objective responses were limited, further exploration of temozolomide may be warranted in children with medulloblastoma and other PNETs, or in patients with low-grade astrocytoma, perhaps in a setting of less pretreatment than the patients in the current study, or in the context of multiagent therapy.

Optimization of quantitative MGMT promoter methylation analysis using pyrosequencing and combined bisulfite restriction analysis

Resistance to chemotherapy is a major complication during treatment of cancer patients. Hypermethylation of the MGMT gene alters DNA repair and is associated with longer survival of glioblastoma patients treated with alkylating agents. Therefore, MGMT promoter methylation plays an important role as a predictive biomarker for chemotherapy resistance. To adopt this established correlation into a molecular diagnosis procedure, we compared and optimized three experimental techniques [combined bisulfite restriction analysis, a primer extension- and denaturing high-performance liquid chromatography-based method named SIRPH (SNuPE ion pair-reverse phase high-performance liquid chromatography), and pyrosequencing] with regard to their accuracy of detecting MGMT promoter methylation. Initially, bisulfite sequencing was used to obtain a comprehensive methylation profile of the MGMT promoter region in 22 glioblastoma samples and in three normal brain controls. Next, we statistically identified CpG sites that best discriminate between methylated and unmethylated MGMT promoters. These results were then used to design optimal combined bisulfite restriction analysis, SIRPH, and pyrosequencing assays for accurate and cost-efficient assessment of MGMT promoter methylation. We compared all three techniques with regard to their reliability and reproducibility on well-characterized tumor samples. The optimized pyrosequencing assay performed best and provides a sensitive, robust, and easy-to-use method for quantitative assessment of MGMT methylation, for both snap-frozen and paraffin-embedded specimens.

Chemoradiotherapy in Malignant Glioma: Standard of Care and Future Directions

Glioma has been considered resistant to chemotherapy and radiation. Recently, concomitant and adjuvant chemoradiotherapy with temozolomide has become the standard treatment for newly diagnosed glioblastoma. Conversely (neo-)adjuvant PCV (procarbazine, lomustine, vincristine) failed to improve survival in the more chemoresponsive tumor entities of anaplastic oligoastrocytoma and oligodendroglioma. Preclinical investigations suggest synergism or additivity of radiotherapy and temozolomide in glioma cell lines. Although the relative contribution of the concomitant and the adjuvant chemotherapy, respectively, cannot be assessed, the early introduction of chemotherapy and the simultaneous administration with radiotherapy appear to be key for the improvement of outcome. Epigenetic inactivation of the DNA repair enzyme methylguanine methyltransferase (MGMT) seems to be the strongest predictive marker for outcome in patients treated with alkylating agent chemotherapy. Patients whose tumors do not have MGMT promoter methylation are less likely to benefit from the addition of temozolomide chemotherapy and require alternative treatment strategies. The predictive value of MGMT gene promoter methylation is being validated in ongoing trials aiming at overcoming this resistance by a dose-dense continuous temozolomide administration or in combination with MGMT inhibitors. Understanding of molecular mechanisms allows for rational targeting of specific pathways of repair, signaling, and angiogenesis. The addition of tyrosine kinase inhibitors vatalanib (PTK787) and vandetinib (ZD6474), the integrin inhibitor cilengitide, the monoclonal antibodies bevacizumab and cetuximab, the mammalian target of rapamycin inhibitors temsirolimus and everolimus, and the protein kinase C inhibitor enzastaurin, among other agents, are in clinical investigation, building on the established chemoradiotherapy regimen for newly diagnosed glioblastoma.