Current Strategies in Treatment of Oligodendroglioma: Evolution of Molecular Signatures of Response

Spatial metabolic heterogeneity of oligodendrogliomas at single-cell resolution

Oligodendrogliomas are a type of rare and incurable gliomas whose metabolic profiles have yet to be fully examined. The present study examined the spatial differences in metabolic landscapes underlying oligodendrogliomas and should provide unique insights into the metabolic characteristics of these uncommon tumors. Single-cell RNA-sequencing expression profiles from 4044 oligodendroglioma cells derived from tumors resected from four locations frontal, temporal, parietal, and frontotemporoinsular) and in which 1p/19q co-deletion and IDH1 or IDH2 mutations were confirmed were computationally analyzed through a robust workflow to elucidate relative differences in metabolic pathway activities among the different locations. Dimensionality reduction using metabolic expression profiles exhibited clustering corresponding to each location subgroup. From the 80 metabolic pathways examined, over 70 pathways had significantly different activity scores between location subgroups. Further analysis of metabolic heterogeneity suggests that mitochondrial oxidative phosphorylation accounts for considerable metabolic variation within the same locations. Steroid and fatty acid metabolism pathways were also found to be major contributors to heterogeneity. Oligodendrogliomas display distinct spatial metabolic differences in addition to intra-location metabolic heterogeneity.

Machine-Learning Approach for Modeling Myelosuppression Attributed to Nimustine Hydrochloride

PURPOSE

A major adverse effect arising from nimustine hydrochloride (ACNU) therapy for brain tumors is myelosuppression. Because its timing and severity vary among individual patients, the ACNU dose level has been adjusted in an empiric manner at individual medical facilities. To our knowledge, ours is the first study to develop a machine-learning approach to estimate myelosuppression through analysis of patient factors before treatment and attempts to clarify the relationship between myelosuppression and hematopoietic stem cells from daily clinical data. Adverse effect prediction will allow ACNU dose adjustment for patients predicted to have decreases in blood cell counts and will enable focused follow-up of patients undergoing chemoradiotherapy.

PATIENTS AND METHODS

Patients were newly pathologically diagnosed with WHO grade 2 or 3 tumors and were treated with ACNU-based chemoradiotherapy. For detailed analysis of the timing and intensity of adverse effects in patients, we developed a data-weighted support vector machine (SVM) based on adverse event criteria (nadir-weighted SVM [NwSVM]). To evaluate the estimation accuracy of blood cell count dynamics, the determination coefficient ( r²) between real and estimated data was calculated by three regression methods: polynomial, SVM, and NwSVM.

RESULTS

Only the NwSVM-based regression enabled estimation of the dynamics of all blood cell types with high accuracy (mean r² = 0.81). The mean timing of nadir arrival estimated using this regression was 35 days for platelets, 41 days for RBCs, 52 days for lymphocytes, 57 days for WBCs, and 62 days for neutrophils.

CONCLUSION

The NwSVM can be used to predict myelosuppression and clearly depicts nadir timing differences between platelets and other blood cells.

Neurosurgical management of adult diffuse low grade gliomas in Canada: a multi-center survey

Adult diffuse low-grade gliomas are slow growing, World Health Organization grade II lesions with insidious onset and ultimate anaplastic transformation. The timing of surgery remains controversial with polarized practices continuing to govern patient management. As a result, the management of these patients is variable. The goal of this questionnaire was to evaluate practice patterns in Canada. An online invitation for a questionnaire including diagnostic, preoperative, perioperative, and postoperative parameters and three cases with magnetic resonance imaging data with questions to various treatment options in these patients was sent to practicing neurosurgeons and trainees. Survey was sent to 356 email addresses with 87 (24.7 %) responses collected. The range of years of practice was less than 10 years 36 % (n = 23), 11–20 years 28 % (n = 18), over 21 years 37 % (n = 24). Twenty-two neurosurgery students of various years of training completed the survey. 94 % (n = 47) of surgeons and trainees (n = 20) believe that we do not know the “right treatment”. 90 % of surgeons do not obtain formal preoperative neurocognitive assessments. 21 % (n = 13) of surgeons and 23 % of trainees (n = 5) perform a biopsy upon first presentation. A gross total resection was believed to increase progression free survival (surgeons: 75 %, n = 46; trainees: 95 %, n = 21) and to increase overall survival (surgeons: 64 %, n = 39, trainees: 68 %, n = 15). Intraoperative MRI was only used by 8 % of surgeons. Awake craniotomy was the procedure of choice for eloquent tumors by 80 % (n = 48) of surgeons and 100 % of trainees. Of those surgeons who perform awake craniotomy 93 % perform cortical stimulation and 38 % performed subcortical stimulation. Using the aid of three hypothetical cases with progressive complexities in tumor eloquence there was a trend for younger surgeons to operate earlier, and use awake craniotomy to obtain greater extent of resection with the aid of cortical stimulation when compared to senior surgeons who still more often preferred a “wait-and-see” approach. Despite the limitations of an online survey study, it has offered insights into the variability in surgeon practice patterns in Canada and the need for a consensus on the workup and surgical management of this disease.

Combination of diffusion tensor imaging and conventional MRI correlates with isocitrate dehydrogenase 1/2 mutations but not 1p/19q genotyping in oligodendroglial tumours

OBJECTIVES

To explore the correlations of conventional MRI (cMRI) and diffusion tensor imaging (DTI) values with the 1p/19 codeletion and IDH mutations in oligodendroglial tumours (OTs).

METHODS

Eighty-four patients with OTs who underwent cMRI and DTI were retrospectively reviewed. The maximal fractional anisotropy and minimal apparent diffusion coefficient (ADC) were measured and compared using the Mann-Whitney U test. Receiver operating characteristic curves, logistic regression analysis and four-table statistics analysis were performed to predict genotypings.

RESULTS

OTs with 1p/19q codeletion or IDH mutations were prone to locate in frontal (P = 0.106 and 0.005, respectively) and insular lobes and were associated with absent or blurry contrast enhancement (P = 0.040 and 0.013, respectively). DTI values showed significant differences between OTs with and without IDH mutations (P < 0.05) but not in OTs with and without 1p/19q loss. The Ki-67 index significantly correlated with IDH mutations (P = 0.002) but not with 1p/19q codeletion. A combination of DTI and cMRI for the identification of IDH mutations resulted in sensitivity, specificity, positive and negative predictive values of 92.2 %, 75.8 %, 93.8 % and 71.1 %, respectively.

CONCLUSIONS

Combination of DTI and cMRI correlates with isocitrate dehydrogenase 1/2 mutations but not 1p/19q genotyping in OTs.

KEY POINTS

• OTs with 1p/19q codeletion were associated with absent or blurry contrast enhancement • OTs with IDH mutations were also associated with absent or blurry contrast enhancement • OTs with IDH mutations were prone to locate in frontal and insular lobes • DTI values can provide a non-invasive method for assessing the IDH status of OTs • A combination of DTI and cMRI correlates with isocitrate dehydrogenase 1/2 mutations.

IDH1 mutation is prognostic for diffuse astrocytoma but not low-grade oligodendrogliomas in patients not treated with early radiotherapy

Despite accumulating knowledge regarding molecular backgrounds, the optimal management strategy for low-grade gliomas remains controversial. One reason is the marked heterogeneity in the clinical course. To establish an accurate subclassification of low-grade gliomas, we retrospectively evaluated isocitrate dehydrogenase-1 (IDH1) mutation in clinical specimens of diffuse astrocytomas (DA) and oligodendroglial tumors separately. No patients were treated with early radiotherapy, and modified PCV chemotherapy was used for postoperative residual tumors or recurrence in oligodendroglial tumors. Immunohistochemical evaluation of IDH status, p53 status, O(6)-methylguanine methyltransferase expression, and the MIB-1 index were performed. The 1p and 19q status was analyzed with fluorescence in situ hybridization. Ninety-four patients were followed for a median period of 8.5 years. For DAs, p53 was prognostic for progression- free survival (PFS) and IDH1 was significant for overall survival (OS) with multivariate analysis. In contrast, for oligodendroglial tumors, none of the parameters was significant for PFS or OS. Thus, the significance of IDH1 mutation is not clear in oligodendroglial tumors that are homogeneously indolent and chemosensitive. In contrast, DAs are heterogeneous tumors including some potentially malignant tumors that can be predicted by examining the IDH1 mutation status.

Signal transducer and activator of transcription 3 promotes angiogenesis and drives malignant progression in glioma

Signal transducer and activator of transcription (STAT) 3 has been described as a "master regulator" of signaling pathways involved in the transition from low-grade glioma (LGG) to high-grade glioma (HGG). Although STAT3 is overexpressed in HGGs, it remains unclear whether its overexpression is sufficient to induce or promote the malignant progression of glioma. To characterize the effect of STAT3 expression on tumor progression in vivo, we expressed the STAT3 gene in glioneuronal progenitor cells in mice. STAT3 was expressed alone or concurrently with platelet-derived growth factor B (PDGFB), a well-described initiator of LGG. STAT3 alone was insufficient to induce tumor formation; however, coexpression of STAT3 with PDGFB in mice resulted in a significantly higher incidence of HGGs than PDGFB alone. The median symptomatic tumor latency in mice coexpressing STAT3 and PDGFB was significantly shorter, and mice that developed symptomatic tumors demonstrated significantly higher expression of phosphorylated STAT3 intratumorally. In HGGs, expression of STAT3 was associated with suppression of apoptosis and an increase in tumor cell proliferation. HGGs induced by STAT3 and PDGFB also displayed frequent foci of necrosis and microvascular proliferation. The expression of CD31 (a marker of endothelial proliferation) was significantly higher in tumors induced by coexpression of STAT3 and PDGFB. When mice injected with PDGFB and STAT3 were treated with a STAT3 inhibitor, median survival increased and the incidence of HGG and CD31 expression decreased significantly. These results demonstrate that STAT3 promotes the malignant progression of glioma. Inhibiting STAT3 expression mitigates tumor progression and improves survival, validating it as a therapeutic target.

MRI apparent diffusion coefficient reflects histopathologic subtype, axonal disruption, and tumor fraction in diffuse-type grade II gliomas

The apparent diffusion coefficient (ADC) determined from MR diffusion tensor imaging (DTI) has shown promise for distinguishing World Health Organization grade II astrocytoma (AS) from the more prognostically favorable grade II oligodendroglioma (OD). Since mixed oligoastrocytomas (OAs) with codeletions in chromosomes 1p and 19q confer prognoses similar to those of OD, we questioned whether a previously determined ADC-based criterion for distinguishing OD and AS would hold on an independent set of gliomas that included OA with codeleted or intact 1p/19q chromosomes. We also questioned whether the ADC is associated with the tumor microstructure. ADC colormaps generated from presurgical DTI scans were used to guide the collection of biopsies from each tumor. The median normalized ADC distinguished OD from AS with 91% sensitivity and 92% specificity. 1p/19q codeleted OAs were always classified as ODs, while 1p/19q intact OAs were always classified as ASs. There were positive associations between the ADC and both the SMI-31 score of axonal disruption and the fraction of tumor cells in the biopsies. The ADC of OD and 1p/19q codeleted OA was more associated with tumor fraction, while the ADC of AS and 1p/19q intact OA was more associated with SMI-31 score. We conclude that our previously determined threshold median ADC can distinguish grade II OD and AS on a new patient cohort and that the distinctions extend to OA with codeleted and intact 1p/19q chromosomes. Further, the ADC in grade II gliomas is associated with the fraction of tumor cells and degree of axonal disruption in tumor subregions.

Bcl-2 promotes malignant progression in a PDGF-B-dependent murine model of oligodendroglioma

A significant subset of gliomas arises after activation of the proproliferative platelet-derived growth factor (PDGF) pathway. The progression of low-grade gliomas to more malignant tumors may be due to oncogenic cellular programs combining with those suppressing apoptosis. Antiapoptotic genes are overexpressed in a variety of cancers, and the antiapoptotic gene, BCL2, is associated with treatment resistance and tumor recurrence in gliomas. However, the impact of antiapoptotic gene expression to tumor formation and progression is unclear. We overexpressed Bcl-2 in a PDGFB-dependent mouse model of oligodendroglioma, a common glioma subtype, to assess its effect in vivo. We hypothesized that the antiapoptotic effect would complement the proproliferative effect of PDGFB to promote tumor formation and progression to anaplastic oligodendroglioma (AO). Here, we show that coexpression of PDGFB and Bcl-2 results in a higher overall tumor formation rate compared to PDGFB alone. Coexpression of PDGFB and Bcl-2 promotes progression to AO with prominent foci of necrosis, a feature of high-grade gliomas. Median tumor latency was shorter in mice injected with PDGFB and Bcl-2 compared to those injected with PDGFB alone. Although independent expression of Bcl-2 was insufficient to induce tumors, suppression of apoptosis (detected by cleaved caspase-3 expression) was more pronounced in AOs induced by PDGFB and Bcl-2 compared to those induced by PDGFB alone. Tumor cell proliferation (detected by phosphohistone H3 activity) was also more robust in high-grade tumors induced by PDGFB and Bcl-2. Our results indicate that suppressed apoptosis enhances oligodendroglioma formation and engenders a more malignant phenotype.

Favorable long-term outcome of low-grade oligodendrogliomas irrespective of 1p/19q status when treated without radiotherapy

Despite the accumulating evidences of high chemosensitivity especially in anaplastic oligodendrogliomas with loss of chromosomes 1p and 19q, the optimal management strategy for low-grade tumors using the 1p/19q information remains controversial. We have treated all low-grade oligodendrogliomas by a chemotherapy-preceding strategy without radiotherapy, and here we analyzed the survival outcomes of 36 consecutive patients in relation to 1p/19q status. The treatment protocol was as follows: (1) simple observation after gross total resection, and (2) modified PCV chemotherapy for postoperative residual tumors or recurrence after total resection. The 1p and 19q status were analyzed by fluorescence in situ hybridization. The median follow-up period was 7.5 years and no patient was lost during the follow-up periods. 1p/19q co-deletion was observed in 72% of the patients, and there was no significant association between 1p/19q co-deletion and chemotherapy response rate. The 5- and 10-year progression-free survival (PFS) rate was 75.1 and 46.9%, respectively, and the median PFS was 121 months for 1p/19q-deleted tumors and 101 months for non-deleted tumors (log-rank test: P = 0.894). Extent of surgery did not affect PFS (P = 0.685). In contrast, the elder patients (>50) had significantly shorter PFS (P = 0.0458). Recurrent tumors were well controlled by chemotherapy irrespective of 1p/19q status, and 35 out of 36 patients survived without receiving radiotherapy. The 5- and 10-year overall survival rates were 100 and 93.8%, respectively. Two of the patients in their sixties (29%) suffered from severe cognitive dysfunctions and marked brain atrophy following chemotherapy alone. These results show that low-grade oligodendrogliomas could be successfully treated by surgical resection and nitrosourea-based chemotherapy alone without radiotherapy irrespective of 1p/19q status.

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.

Gliomas with 1p/19q codeletion: a.k.a. oligodendroglioma

Today, treatment recommendations for patients with all types of gliomas are based on light microscopic evaluation of tumor tissue with no allowance for genetic variability. Oligodendrogliomas are treated in a uniform manner with, as yet, no unique therapeutic approach or targeted therapy for those harboring a codeletion of chromosomes 1p and 19q. Surgical resection and radiotherapy are the standards-of-care for patients with oligodendrogliomas. Surgery improves symptoms, especially headache or seizures, and radiotherapy controls tumor growth for most patients. By extrapolation from randomized trials of glioblastoma, radiotherapy likely prolongs survival. Uncertainties persist about the timing of radiotherapy in the management of patients with low-grade oligodendrogliomas, but a superior antitumor treatment has yet to emerge. That said, the recognition that oligodendrogliomas with 1p/19q loss are sensitive to current therapies and slowly growing is already influencing our management of patients with this type of glioma, spawning trials in which patients are selected by molecular signature.

[Fluorescence in situ hybridization. A new diagnostic dimension in cytology]

Fluorescence in situ hybridization (FISH) is a powerful method for the identification of chromosomal aberrations to improve the diagnostic performance of cytology. FISH is applicable to almost any type of cytological specimen irrespective of cell type, staining or fixation modality. Multi-target tests for the simultaneous analysis of four chromosomes or chromosomal loci improves the sensitivity of cytological diagnosis in bladder and lung cancer and is most helpful in equivocal cytology. FISH also allows a reliable distinction between malignant mesothelioma and reactive mesothelial cells. Specific translocations can easily be detected by FISH for precise diagnosis of lymphomas and sarcomas. Testing for HER-2 amplification has become a standard method to select patients with breast cancer for therapy with trastuzumab. Co-analysis of HPV and selected genes could become a useful approach in gynecological cytology. The spectrum of diagnostic FISH applications is continuously growing.

Identification of genomic aberrations associated with shorter overall survival in patients with oligodendroglial tumors

Deletions on chromosomes 1p and 19q are associated with favorable prognosis in patients with oligodendroglial tumors. The aim of our study was to identify additional genomic aberrations linked to patient survival. We performed a genome-wide screen for genomic imbalances by comparative genomic hybridization on tumors from 70 patients, including 40 oligodendrogliomas, 30 oligoastrocytomas (21 WHO grade II tumors, 49 WHO grade III tumors). Data were correlated with overall patient survival (OS, median follow-up: 5.8 years). The most frequent aberrations were losses on chromosome 19q (64%), 1p (59%), 9p (26%), 4q (21%), 10q (19%), 18q (17%); gains on 7q (24%), 19p (19%), 7p (17%). In univariate analyses, combined 1p/19q and 19q loss were significantly associated with longer OS, and gains on 7, 8q, 19q, 20, losses on 9p, 10, 18q, Xp with shorter OS. Multivariate analyses showed the most significant prognostic factors for OS of patients with any oligodendroglial tumor to be WHO grade [odds ratio (OR) 8], 7p gain (OR 6), 9p loss (OR 3); for OS of patients with anaplastic tumors to be 7p gain (OR 10), 8q gain (OR 5), 18q loss (OR 3). Patients with anaplastic oligodendroglial tumors containing one or more prognostically unfavorable genomic aberration had a poor outcome independent of the 1p/19q status. In summary, we identified several independent genomic markers of shorter survival in patients with oligodendroglial tumors. Thus, molecular diagnostic testing, which is usually restricted to 1p/19q deletion analysis, may need to be refined by additionally assessing the prognostically unfavorable genomic aberrations identified.

Longitudinal assessment of genetic and epigenetic markers in oligodendrogliomas

PURPOSE

Because little is known about the evolution of genetic and epigenetic changes that occur during tumor progression in oligodendrogliomas, we evaluated these changes in paired early and progressive oligodendrogliomas.

EXPERIMENTAL DESIGN

1p36, 19q13, 10q22-26, and O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation status were assessed in 46 paired early and progressive oligodendrogliomas from 23 patients.

RESULTS

In early tumors, 60.8% were of low grade compared with only 17% low-grade tumors at recurrence. Of 17 early tumors described as pure oligodendrogliomas, 76.5% remained in this lineage, regardless of their grade, whereas others changed to astrocytic tumors. Oligoastrocytic tumors had a significantly higher tendency to transform to astrocytic tumors. All pure oligodendrogliomas with 1p/19q codeletions remained phenotypically unchanged, unlike mixed tumors with codeletions, of which 83% changed their cell lineage. Of tumors with early 1p deletion, 80% remained oligodendroglial at progression, whereas 75% of tumors with an intact 1p changed to astrocytic phenotype. 10q loss was uncommon in both early and progressive tumors. The proportional gain in methylation at progression was 31% for tumors with early 1p deletion, unlike tumors with an intact 1p, which had an 87.5% gain of methylation at progression.

CONCLUSIONS

Pure oligodendrogliomas with 1p/19q deletion tend to retain their cell phenotype and genetic profile unlike tumors with no deletions or mixed histology. MGMT promoter methylation is more pronounced at tumor progression, particularly in tumors with an intact 1p. These observations suggest that MGMT promoter methylation is a late event in progressive oligodendrogliomas, and therefore, their chemosensitivity is not necessarily related to MGMT methylation status.

Survey of treatment recommendations for anaplastic oligodendroglioma

Anaplastic oligodendroglioma is a malignant brain tumor uniquely sensitive to treatment with both chemotherapy and radiotherapy. There are few prospective clinical trials for newly diagnosed patients and multiple approaches to the treatment of these patients. This study explored the recommended treatment offered by experts in neuro-oncology. A Web-based survey was developed and distributed to 800 members of the Society of Neuro-Oncology (SNO) who had an e-mail address listed with SNO. Questions addressed use of molecular genetic information and treatment recommendations. A total of 99 clinical SNO members (20%) responded. The majority reported practicing at an academic center in the United States. Two-thirds of respondents see more than five patients with newly diagnosed anaplastic oligodendroglioma annually. Molecular genetic testing was requested for more than 75% of patients, and the results significantly influenced treatment recommendations (p = 0.000003). Regardless of molecular genetic status, the most commonly recommended treatment was the use of concurrent temozolomide and radiotherapy followed by adjuvant temozolomide (18%-34%). The current survey demonstrates that although neuro-oncologists have embraced the use of molecular genetic studies in newly diagnosed anaplastic oligodendroglioma, treatment recommendations vary widely and are often independent of the molecular data.

Application and interpretation of FISH in biomarker studies

Emerging genomic and proteomic data is creating new opportunities to identify novel biomarkers that will have pathway-specific therapeutic impact on cancer progression. Molecular cytogenetic and fluorescence in situ hybridization (FISH) methods have been primarily used in discovery genetic research laboratories until recently. New automated analytical platforms based on FISH technologies and tissue microarray methods are providing a rapid means to determine the impact of consistent genomic aberrations in clinical trials, and in studies designed to investigate differential chemotherapeutic response.

Glioma therapy in adults

BACKGROUND

Gliomas are the most common type of primary brain tumor. Nearly two-thirds of gliomas are highly malignant lesions that account for a disproportionate share of brain tumor-related morbidity and mortality. Despite recent advances, two-year survival for glioblastoma with optimal therapy is less than 30%. Even among patients with low-grade gliomas that confer a relatively good prognosis, treatment is almost never curative.

REVIEW SUMMARY

Surgery and radiation have been the mainstays of therapy for most glioma patients, but temozolomide chemotherapy has recently been proven to prolong overall survival in patients with glioblastoma. Intriguing data suggests that activity of O6-methylguanine-DNA methyltransferase (MGMT), in tumor cells may predict responsiveness to temozolomide and other alkylating agents. Novel treatment approaches, especially targeted molecular therapies against critical components of glioma signaling pathways, appear promising in preliminary studies. Optimal treatment for patients with low-grade gliomas has yet to be determined. Advances in oligodendroglioma biology have identified loss of chromosomes 1p and 19q as powerful indicators of a favorable prognosis. These same changes may predict response to chemotherapy.

CONCLUSIONS

Though the prognosis for many patients with gliomas is poor, the last decade produced a number of important advances, some of which have translated directly into survival benefits. Rapid progress in the field of glioma molecular biology continues to identify therapeutic targets and provide hope for the future of this challenging disease.

Chemotherapeutic options for primary brain tumors

Malignant gliomas are the most common primary brain tumors. Despite intensive clinical investigation and many novel therapeutic approaches, treatment for most primary brain tumors remains inadequate. Most are associated with a high rate of recurrence after primary therapy and a dismal outcome following recurrence. Surgery and radiation remain the primary modalities of therapy for malignant brain tumors. The role of chemotherapy in malignant gliomas, especially glioblastoma multiforme, has been inconclusive. However, a recent trial by the European Organisation for Research and Treatment of Cancer and the National Cancer Institute of Canada combining radiation therapy with temozolomide for newly diagnosed glioblastoma patients showed a significantly improved survival benefit over radiation therapy alone. In addition to this encouraging progress, recent experience has shown that selected malignant brain tumors--for example, anaplastic oligodendrogliomas, primary central nervous system lymphomas, medulloblastomas, and intracranial germ cell tumors--are often highly responsive to chemotherapy. Molecular genetic studies are becoming indispensable aids in the diagnosis and treatment of the malignant gliomas. For example, we have learned that allelic loss of chromosome 1p is a significant predictor of chemosensitivity, whereas combined loss of chromosomes 1p and 19q is a strong predictor of chemosensitivity, progression-free survival, and overall survival in patients with anaplastic oligodendroglioma. Similarly, MGMT promoter methylation is associated with more frequent responses and longer survival in patients with glioblastoma multiforme receiving temozolomide-based therapy. These and other recent advances have led to the development and testing of several novel chemotherapeutic and molecular-targeted agents. Several different approaches and modalities to improve the efficacy of chemotherapy (eg, MGMT promoter methylation) are currently under way. Clinical trials implementing angiogenesis inhibitors, biologic modifiers, or molecular-targeted therapies are also actively being investigated.

Recent advances in the medical therapy of high-grade gliomas

Malignant glial neoplasms, including glioblastoma, are amongst the most devastating and intractable of solid tumors. Until recently the standard of care for newly diagnosed glioblastoma was surgical resection to the extent feasible followed by conventional fractionated radiotherapy. When administered for disease progression, chemotherapy had modest benefit and its use in the adjuvant setting was controversial. Temozolomide, an oral alkylating chemotherapeutic agent, has now been demonstrated to increase survival time in patients with newly diagnosed glioblastoma when used concurrently with radiotherapy and as adjuvant or maintenance treatment for six cycles thereafter. Correlative molecular studies suggested that the benefit of temozolomide is largely restricted to patients whose tumor has silenced the gene for methylguanine methyltransferase, a repair enzyme implicated in resistance to alkylator chemotherapy. Use of temozolomide chemotherapy upfront in the management of glioblastoma is now considered the standard of care. This significant advance has also stimulated development of therapeutic strategies that incorporate temozolomide, and other agents, in the initial management of most high-grade gliomas. Furthermore, our increased understanding of the molecular derangements that underlie gliomagenesis has identified a number of putative molecular targets against which novel therapeutics have been tested with encouraging preliminary results. Finally, the challenges presented by the blood–brain barrier to adequate drug delivery have stimulated the development of unique locoregional delivery techniques that are currently undergoing clinical evaluation. This review summarizes these recent advances, and speculates on how the field is likely to evolve in the near future.

Chemotherapy in the treatment of malignant gliomas

Malignant gliomas are one of the most difficult tumors to treat, with only modest advances being made in the past few decades. Surgery and radiation have had the greatest impact, increasing survival. Chemotherapy modestly increases survival. The use of chemotherapy in the treatment of malignant gliomas is the focus of this paper and the more commonly used agents at diagnosis and relapse are reviewed. Since most patients fail first-, second- and even third-line agents that are commercially available, some of the more relevant new biological compounds will also be discussed. As treatments for brain tumors evolve, it is likely that optimal therapies will come from combination therapies that incorporate target-specific and chemotherapeutic agents.

Diffusely infiltrative low-grade gliomas in adults

Diffusely infiltrating low-grade gliomas (LGGs) include astrocytomas, oligodendrogliomas, and mixed oligoastrocytomas (WHO grade 2). Due to the routine use of magnetic resonance imaging, there is an increasing need to formulate treatment guidelines for patients with LGGs. However, there is little consensus about the optimal treatment strategy for diffusely infiltrative LGGs, and the clinical management of LGGs is one of the most controversial areas in neurooncology. Although the standard of care has not been established, several randomized trials are beginning to provide some answers. Furthermore, laboratory correlative studies are defining subsets of LGG that may identify patients with better prognoses and increased chance of responding to therapy. This article reviews the most recent data regarding the treatment of LGG, emphasizing evidenced based approaches from current clinical trials.