Isocitrate dehydrogenase (IDH) mutant gliomas: A Society for Neuro-Oncology (SNO) consensus review on diagnosis, management, and future directions.

Isocitrate dehydrogenase (IDH) mutant gliomas are the most common adult, malignant primary brain tumors diagnosed in patients younger than 50, constituting an important cause of morbidity and mortality. In recent years, there has been significant progress in understanding the molecular pathogenesis and biology of these tumors, sparking multiple efforts to improve their diagnosis and treatment. In this consensus review from the Society for Neuro-Oncology (SNO), the current diagnosis and management of IDH-mutant gliomas will be discussed. In addition, novel therapies, such as targeted molecular therapies and immunotherapies, will be reviewed. Current challenges and future directions for research will be discussed.

Phase I Study of High-Dose L-methylfolate in Combination with Temozolomide and Bevacizumab in Recurrent IDH wild-type High-Grade Glioma.

Purpose: IDH mutations in low-grade gliomas (LGGs) results in improved survival and DNA hypermethylation compared to IDH wild-type LGGs. IDH-mutant LGGs become hypomethylated during progression. It's uncertain if methylation changes occur during IDH wild-type GBM progression and if the methylome can be reprogrammed. This phase I study evaluated the safety, tolerability, efficacy and methylome changes after L-methylfolate (LMF) treatment, in combination with temozolomide and bevacizumab in patients with recurrent high-grade glioma. Patients and Methods: Fourteen patients total, 13 with GBM, one with anaplastic astrocytoma, all IDH wild-type were enrolled in the study. All patients received LMF at either 15, 30, 60, or 90 mg daily plus temozolomide (75mg/m2 5 days per month) and bevacizumab (10mg/kg every two weeks). Results: No MTD was identified. LMF treated had mOS of 9.5 months (95% CI, 9.1-35.4) comparable to bevacizumab historical control 8.6 months (95% CI, 6.8-10.8). Six patients treated with LMF survived more than 650 days. Across all treatment doses the most adverse events were diarrhea (7%, 1 patient, grade 2), reflux (7%, 1 patient, grade 2), and dysgeusia (7%, 1 patient, grade 2). In the six brains donated at death, there was a 25% increase in DNA methylated CpGs compared to the paired initial tumor. Conclusions: LMF in combination with temozolomide and bevacizumab was well tolerated in patients with recurrent IDH wild-type high-grade glioma. This small study did not establish a superior efficacy with addition of LMF compared to standard bevacizumab therapy, however, this study did show methylome reprogramming in high-grade glioma.

Circulating Micrornas Predict Survival of Patients with Tumors of Glial Origin.

The World Health Organization has recently introduced molecular prognostic-diagnostic biomarkers in the classification of Central Nervous System (CNS) tumors. In order to characterize subclasses of tumors that cannot find a precise location in the current classification, and, or cannot be tested because of scant material, it is important to find new molecular biomarkers in tissue and, or biological fluid samples. In this study, we identified serum microRNAs that could serve as biomarkers for the diagnosis and prognosis of patients with tumors of glial origin. We retrospectively analyzed microRNA expression in the serum extracellular vesicles of patients with tumors of glial origin. Extracellular vesicles RNA was analyzed by Nanostring. qRT-PCR confirmed 6 overexpressed microRNAs: hsa-miR-4443, hsa-miR-422a, hsa-miR-494-3p, hsa-miR-502-5p, hsa-miR-520f-3p, and hsa-miR-549a. Hsa-miR-4443 was the only microRNA that showed significant differences in most comparisons. In situ hybridization (ISH), confirmed that our signature was mostly expressed in cancer cells. Importantly, hsa-miR-549a and hsa-miR-502-5p expression predicted prognosis in patients with tumors of glial origin. Although more studies are needed, we demonstrated that serum vesicles microRNA profiles are promising diagnostic and prognostic molecular biomarkers that will find an actual application in the clinical practice of CNS tumors.

Glioma Groups Based on 1p/19q, IDH, and TERT Promoter Mutations in Tumors.

BACKGROUND: The prediction of clinical behavior, response to therapy, and outcome of infiltrative glioma is challenging. On the basis of previous studies of tumor biology, we defined five glioma molecular groups with the use of three alterations: mutations in the TERT promoter, mutations in IDH, and codeletion of chromosome arms 1p and 19q (1p/19q codeletion). We tested the hypothesis that within groups based on these features, tumors would have similar clinical variables, acquired somatic alterations, and germline variants. METHODS: We scored tumors as negative or positive for each of these markers in 1087 gliomas and compared acquired alterations and patient characteristics among the five primary molecular groups. Using 11,590 controls, we assessed associations between these groups and known glioma germline variants. RESULTS: Among 615 grade II or III gliomas, 29% had all three alterations (i.e., were triple-positive), 5% had TERT and IDH mutations, 45% had only IDH mutations, 7% were triple-negative, and 10% had only TERT mutations; 5% had other combinations. Among 472 grade IV gliomas, less than 1% were triple-positive, 2% had TERT and IDH mutations, 7% had only IDH mutations, 17% were triple-negative, and 74% had only TERT mutations. The mean age at diagnosis was lowest (37 years) among patients who had gliomas with only IDH mutations and was highest (59 years) among patients who had gliomas with only TERT mutations. The molecular groups were independently associated with overall survival among patients with grade II or III gliomas but not among patients with grade IV gliomas. The molecular groups were associated with specific germline variants. CONCLUSIONS: Gliomas were classified into five principal groups on the basis of three tumor markers. The groups had different ages at onset, overall survival, and associations with germline variants, which implies that they are characterized by distinct mechanisms of pathogenesis. (Funded by the National Institutes of Health and others.).

Evolution of DNA repair defects during malignant progression of low-grade gliomas after temozolomide treatment.

Temozolomide (TMZ) increases the overall survival of patients with glioblastoma (GBM), but its role in the clinical management of diffuse low-grade gliomas (LGG) is still being defined. DNA hypermethylation of the O (6) -methylguanine-DNA methyltransferase (MGMT) promoter is associated with an improved response to TMZ treatment, while inactivation of the DNA mismatch repair (MMR) pathway is associated with therapeutic resistance and TMZ-induced mutagenesis. We previously demonstrated that TMZ treatment of LGG induces driver mutations in the RB and AKT-mTOR pathways, which may drive malignant progression to secondary GBM. To better understand the mechanisms underlying TMZ-induced mutagenesis and malignant progression, we explored the evolution of MGMT methylation and genetic alterations affecting MMR genes in a cohort of 34 treatment-naïve LGGs and their recurrences. Recurrences with TMZ-associated hypermutation had increased MGMT methylation compared to their untreated initial tumors and higher overall MGMT methylation compared to TMZ-treated non-hypermutated recurrences. A TMZ-associated mutation in one or more MMR genes was observed in five out of six TMZ-treated hypermutated recurrences. In two cases, pre-existing heterozygous deletions encompassing MGMT, or an MMR gene, were followed by TMZ-associated mutations in one of the genes of interest. These results suggest that tumor cells with methylated MGMT may undergo positive selection during TMZ treatment in the context of MMR deficiency.

Variants near TERT and TERC influencing telomere length are associated with high-grade glioma risk.

Glioma, the most common central nervous system cancer in adults, has poor prognosis. Here we identify a new SNP associated with glioma risk, rs1920116 (near TERC), that reached genome-wide significance (Pcombined = 8.3 × 10(-9)) in a meta-analysis of genome-wide association studies (GWAS) of high-grade glioma and replication data (1,644 cases and 7,736 controls). This region has previously been associated with mean leukocyte telomere length (LTL). We therefore examined the relationship between LTL and both this new risk locus and other previously established risk loci for glioma using data from a recent GWAS of LTL (n = 37,684 individuals). Alleles associated with glioma risk near TERC and TERT were strongly associated with longer LTL (P = 5.5 × 10(-20) and 4.4 × 10(-19), respectively). In contrast, risk-associated alleles near RTEL1 were inconsistently associated with LTL, suggesting the presence of distinct causal alleles. No other risk loci for glioma were associated with LTL. The identification of risk alleles for glioma near TERC and TERT that also associate with telomere length implicates telomerase in gliomagenesis.

Genetic variants in telomerase-related genes are associated with an older age at diagnosis in glioma patients: evidence for distinct pathways of gliomagenesis.

BACKGROUND: Genome-wide association studies have implicated single nucleotide polymorphisms (SNPs) in 7 genes as glioma risk factors, including 2 (TERT, RTEL1) involved in telomerase structure/function. We examined associations of these 7 established glioma risk loci with age at diagnosis among patients with glioma. METHODS: SNP genotype data were available for 2286 Caucasian glioma patients from the University of California, San Francisco (n = 1434) and the Mayo Clinic (n = 852). Regression analyses were performed to test for associations between "number of risk alleles" and "age at diagnosis," adjusted for sex and study site and stratified by tumor grade/histology where appropriate. RESULTS: Four SNPs were significantly associated with age at diagnosis. Carrying a greater number of risk alleles at rs55705857 (CCDC26) and at rs498872 (PHLDB1) was associated with younger age at diagnosis (P = 1.4 × 10(-22) and P = 9.5 × 10(-7), respectively). These SNPs are stronger risk factors for oligodendroglial tumors, which tend to occur in younger patients, and their association with age at diagnosis varied across tumor subtypes. In contrast, carrying more risk alleles at rs2736100 (TERT) and at rs6010620 (RTEL1) was associated with older age at diagnosis (P = 6.2 × 10(-4) and P = 2.5 × 10(-4), respectively). These SNPs are risk factors for all glioma grades/histologies, and their association with age at diagnosis was consistent across tumor subgroups. CONCLUSIONS: Carrying a greater number of risk alleles might be expected to decrease age at diagnosis. However, glioma susceptibility conferred by variation in telomerase-related genes did not follow this pattern. This supports the hypothesis that telomerase-related mechanisms of telomere maintenance are more associated with gliomas that develop later in life than those utilizing telomerase-independent mechanisms (ie, alternative lengthening of telomeres).

Phase II study of pre-irradiation chemotherapy for childhood intracranial ependymoma. Children's Cancer Group protocol 9942: a report from the Children's Oncology Group.

PURPOSE: Standard therapy for childhood intracranial ependymoma is maximal tumor resection followed by involved-field irradiation. Although not used routinely, chemotherapy has produced objective responses in ependymoma, both at recurrence and in infants. Because the presence of residual tumor following surgery is consistently associated with inferior outcome, the potential impact of pre-irradiation chemotherapy was investigated. METHODS: Between 1995 and 1999, the Children's Cancer Group undertook a Phase II trial of pre-irradiation chemotherapy in children 3-21 years of age with intracranial ependymoma and radiological evidence of post-operative residual tumor. RESULTS: Of 84 patients, 41 had residual tumor, and were given four cycles of cisplatin-based chemotherapy prior to irradiation. Of 35 patients fully evaluable for response to chemotherapy, 14 (40%) demonstrated complete response, 6 (17%) partial response, 10 (29%) minor response or stable disease, and 5 (14%) demonstrated progressive tumor growth. For the entire group, 5-year overall survival (OS) and event-free survival (EFS) was 71 ± 6%, and 57 ± 6%, respectively. The pre-irradiation chemotherapy group demonstrated EFS comparable to that of patients with no residual tumor who received irradiation alone (55 ± 8% vs. 58 ± 9%, P = 0.45). Any benefit of chemotherapy was restricted to patients with greater than 90% tumor resection. CONCLUSIONS: Children with near total resection of ependymoma may benefit from pre-irradiation chemotherapy. Patients with subtotal resection have inferior outcome despite responses to chemotherapy, and should be considered for second-look surgery prior to irradiation. Pediatr Blood Cancer 2012; 59: 1183-1189. © 2012 Wiley Periodicals, Inc.

The potential origin of glioblastoma initiating cells.

Despite intensive clinical and laboratory research and effort, Glioblastoma remains the most common and invariably lethal primary cancer of the central nervous system. The identification of stem cell and lineage-restricted progenitor cell populations within the adult human brain in conjunction with the discovery of stem-like cells derived from gliomas which are themselves tumorigenic and have been shown to have properties of self-renewal and multipotency, has led to the hypothesis that this population of cells may represent glioma initiating cells. Extensive research characterizing the anatomic distribution and phenotype of neural stem cells in the adult brain, and the genetic underpinnings needed for malignant transformation may ultimately lead to the identification of the cellular origin for glioblastoma. Defining the cellular origin of this lethal disease may ultimately provide new therapeutic targets and modalities finally altering an otherwise bleak outcome for patients with glioblastoma.

Adjuvant enoxaparin therapy may decrease the incidence of postoperative thrombotic events though does not increase the incidence of postoperative intracranial hemorrhage in patients with meningiomas.

Patients with brain tumors including intracranial meningiomas are at increased risk for developing deep vein thrombosis (DVTs) and suffering thromboembolic events (VTEs). Many surgeons are concerned that early use of low dose enoxaparin may increase the risk of intracranial hemorrhage which outweighs the benefit of DVT/VTE reduction. We aimed to address concerns around the use of enoxaparin after meningioma resection in the development of postoperative intracranial hemorrhages and DVT/VTEs. This is a retrospective review of 86 patients with intracranial meningiomas who underwent craniectomy and surgical resection of the mass, treated by one attending surgeon at UCSF Medical Center between 2000 and 2005. Within 48 h after surgery patients treated 2003-2005 routinely received enoxaparin therapy unless there was documented intracranial hemorrhage, lumbar subarachnoid drain, enoxaparin hypersensitivity, or thrombocytopenia (n = 24). These were compared to a cohort treated 2000-2002 who did not receive the drug (n = 62). Exclusion criteria were prior VTEs or coagulopathies. The groups were similar in tumor and surgical characteristics. Enoxaparin therapy did not increase the incidence of intracranial hemorrhage following surgical meningioma resection and the incidence of DVTs/VTEs was 0% (n = 0) versus 4.8% (n = 3) in the non-enoxaparin group. Results did not reach statistical significance. In this retrospective study, postoperative administration of enoxaparin following meningioma resection does not increase the risk of intracranial hematoma though enoxaparin administration may slightly decrease the incidence of post-surgical thromboembolic events. Due to study design and power, we were not able to demonstrate DVT/VTE reduction with statistical significance.

Phase I trial of gross total resection, permanent iodine-125 brachytherapy, and hyperfractionated radiotherapy for newly diagnosed glioblastoma multiforme.

PURPOSE: To evaluate the feasibility of gross total resection and permanent I-125 brachytherapy followed by hyperfractionated radiotherapy for patients with newly diagnosed glioblastoma. METHODS AND MATERIALS: From April 1999 to May 2002, 21 patients with glioblastoma multiforme were enrolled on a Phase I protocol investigating planned gross total resection and immediate placement of permanent I-125 seeds, followed by postoperative hyperfractionated radiotherapy to a dose of 60 Gy at 100 cGy b.i.d., 5 days per week. Median age and Karnofsky performance status were 50 years (range, 32-65 years) and 90 (range, 70-100), respectively. Toxicity was assessed according to Radiation Therapy Oncology Group criteria. RESULTS: Eighteen patients completed treatment according to protocol. The median preoperative tumor volume on magnetic resonance imaging was 18.6 cm(3) (range, 4.4-41.2 cm(3)). The median brachytherapy dose measured 5 mm radially outward from the resection cavity was 400 Gy (range, 200-600 Gy). Ten patients underwent 12 reoperations, with 11 of 12 reoperations demonstrating necrosis without evidence of tumor. Because of high toxicity, the study was terminated early. Median progression-free survival and overall survival were 57 and 114 weeks, respectively, but not significantly improved compared with historical patients treated at University of California, San Francisco, with gross total resection and radiotherapy without brachytherapy. CONCLUSIONS: Treatment with gross total resection and permanent I-125 brachytherapy followed by hyperfractionated radiotherapy as performed in this study results in high toxicity and reoperation rates, without demonstrated improvement in survival.

Cellular composition and cytoarchitecture of the adult human subventricular zone: a niche of neural stem cells.

The lateral wall of the lateral ventricle in the human brain contains neural stem cells throughout adult life. We conducted a cytoarchitectural and ultrastructural study in complete postmortem brains (n = 7) and in postmortem (n = 42) and intraoperative tissue (n = 43) samples of the lateral walls of the human lateral ventricles. With varying thickness and cell densities, four layers were observed throughout the lateral ventricular wall: a monolayer of ependymal cells (Layer I), a hypocellular gap (Layer II), a ribbon of cells (Layer III) composed of astrocytes, and a transitional zone (Layer IV) into the brain parenchyma. Unlike rodents and nonhuman primates, adult human glial fibrillary acidic protein (GFAP)+ subventricular zone (SVZ) astrocytes are separated from the ependyma by the hypocellular gap. Some astrocytes as well as a few GFAP-cells in Layer II in the SVZ of the anterior horn and the body of the lateral ventricle appear to proliferate based on proliferating cell nuclear antigen (PCNA) and Ki67 staining. However, compared to rodents, the adult human SVZ appears to be devoid of chain migration or large numbers of newly formed young neurons. It was only in the anterior SVZ that we found examples of elongated Tuj1+ cells with migratory morphology. We provide ultrastructural criteria to identify the different cells types in the human SVZ including three distinct types of astrocytes and a group of displaced ependymal cells between Layers II and III. Ultrastructural analysis of this layer revealed a remarkable network of astrocytic and ependymal processes. This work provides a basic description of the organization of the adult human SVZ.

Preradiation chemotherapy in primary high-risk brainstem tumors: phase II study CCG-9941 of the Children's Cancer Group.

PURPOSE: This Children's Cancer Group group-wide phase II trial evaluated the efficacy and toxicity of two chemotherapy arms administered before hyperfractionated external-beam radiotherapy (HFEBRT). PATIENTS AND METHODS: Thirty-two patients with newly diagnosed brainstem gliomas were randomly assigned to regimen A and 31 to regimen B. Regimen A comprised three courses of carboplatin, etoposide, and vincristine; regimen B comprised cisplatin, etoposide, cyclophosphamide, and vincristine. Both arms included granulocyte colony-stimulating factor. Patients were evaluated by magnetic resonance imaging after induction chemotherapy and HFEBRT at a dose of 72 Gy. RESULTS: Ten percent +/- 5% of regimen A patients objectively responded to chemotherapy. For combined induction and radiotherapy, 27% +/- 9% of patients improved. The neuroradiographic response rate for regimen B was 19% +/- 8% for chemotherapy and 23% +/- 9% after HFEBRT. Response rates were not statistically significant between regimens after induction or chemotherapy/HFEBRT. Event-free survival was 17% +/- 5% (estimate +/- SE) at 1 year and 6% +/- 3% at 2 years. Survival was significantly longer among patients who responded to chemotherapy (P <.05). Among patients who received regimen A induction, grades 3 and 4 leukopenia were observed in 50% to 65%, with one toxicity-related death. For regimen B, severe leukopenia occurred in 86% to 100%, with febrile neutropenia in 48% to 60% per course. CONCLUSION: Neither chemotherapy regimen meaningfully improved response rate, event-free survival, or overall survival relative to previous series of patients with brainstem gliomas who received radiotherapy with or without chemotherapy.