Andrew D. Norden

Exciting New Advances in Neuro-Oncology The Avenue to a Cure for Malignant Glioma

Malignant gliomas are the most common and deadly brain tumors. Nevertheless, survival for patients with glioblastoma, the most aggressive glioma, although individually variable, has improved from an average of 10 months to 14 months after diagnosis in the last 5 years due to improvements in the standard of care. Radiotherapy has been of key importance to the treatment of these lesions for decades, and the ability to focus the beam and tailor it to the irregular contours of brain tumors and minimize the dose to nearby critical structures with intensity‐modulated or image‐guided techniques has improved greatly. Temozolomide, an alkylating agent with simple oral administration and a favorable toxicity profile, is used in conjunction with and after radiotherapy. Newer surgical techniques, such as fluorescence‐guided resection and neuroendoscopic approaches, have become important in the management of malignant gliomas. Furthermore, new discoveries are being made in basic and translational research, which are likely to improve this situation further in the next 10 years. These include agents that block 1 or more of the disordered tumor proliferation signaling pathways, and that overcome resistance to already existing treatments. Targeted therapies such as antiangiogenic therapy with antivascular endothelial growth factor antibodies (bevacizumab) are finding their way into clinical practice. Large‐scale research efforts are ongoing to provide a comprehensive understanding of all the genetic alterations and gene expression changes underlying glioma formation. These have already refined the classification of glioblastoma into 4 distinct molecular entities that may lead to different treatment regimens. The role of cancer stem‐like cells is another area of active investigation. There is definite hope that by 2020, new cocktails of drugs will be available to target the key molecular pathways involved in gliomas and reduce their mortality and morbidity, a positive development for patients, their families, and medical professionals alike. CA Cancer J Clin 2010;60:166–193.

Bevacizumab for recurrent malignant gliomas: efficacy, toxicity, and patterns of recurrence.

Background: Bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor, may have activity in recurrent malignant gliomas. At recurrence some patients appear to develop nonenhancing infiltrating disease rather than enhancing tumor. Methods: We retrospectively reviewed 55 consecutive patients with recurrent malignant gliomas who received bevacizumab and chemotherapy to determine efficacy, toxicity, and patterns of recurrence. Using a blinded, standardized imaging review and quantitative volumetric analysis, the recurrence patterns of patients treated with bevacizumab were compared to recurrence patterns of 19 patients treated with chemotherapy alone. Results: A total of 2.3% of patients had a complete response, 31.8% partial response, 29.5% minimal response, and 29.5% had stable disease. Median time to radiographic progression was 19.3 weeks. Six-month progression-free survival (PFS) was 42% for patients with glioblastoma and 32% for patients with anaplastic glioma. In 23 patients who progressed on their initial therapy, bevacizumab was continued and the concurrent chemotherapy agent changed. In no case did the change produce a radiographic response, but two patients had prolonged PFS of 20 and 31 weeks. Recurrence pattern analysis identified a significant increase in the volume of infiltrative tumor relative to enhancing tumor in bevacizumab responders. Conclusions: Combination therapy with bevacizumab and chemotherapy is well-tolerated and active against recurrent malignant gliomas. At recurrence, continuing bevacizumab and changing the chemotherapy agent provided long-term disease control only in a small subset of patients. Bevacizumab may alter the recurrence pattern of malignant gliomas by suppressing enhancing tumor recurrence more effectively than it suppresses nonenhancing, infiltrative tumor growth.

Antiangiogenic therapies for high-grade glioma

High-grade gliomas (HGGs) are vascular tumors that represent attractive targets for antiangiogenic therapies. In this Review, we present the rationale and clinical trial evidence for targeting angiogenesis in HGGs, focusing predominantly on agents that target vascular endothelial growth factor (VEGF) and its receptors. Bevacizumab, a humanized monoclonal antibody against VEGF, was recently approved by the FDA for treatment of recurrent glioblastoma. Bevacizumab prolongs progression-free survival and controls peritumoral edema, but its effects on overall survival remain to be determined. Other inhibitors of VEGF, VEGF receptors and other proangiogenic signaling pathways are being evaluated. Antiangiogenic therapies are well tolerated, although potentially serious adverse events can occasionally occur, and resistance to antiangiogenic therapy inevitably develops. Mechanisms of resistance include upregulation of alternative proangiogenic pathways, and increased perivascular tumor growth. Tumor progression on antiangiogenic agents is a challenging problem for which no effective salvage therapy has been identified. Combining these agents with radiation therapy, cytotoxic chemotherapy, other targeted molecular agents, or anti-invasion therapies could be helpful. The international Response Assessment in Neuro-Oncology Working Group has developed consensus treatment response criteria for HGG that account for the complex effects of antiangiogenic drugs.

Novel anti-angiogenic therapies for malignant gliomas

BACKGROUND Despite optimum treatment with surgery, radiation therapy, and chemotherapy, most patients with malignant glioma have a poor prognosis. Malignant gliomas are vascular tumours that produce vascular endothelial growth factor (VEGF), which is an important mediator of angiogenesis. Preclinical data indicate that angiogenesis is essential for the proliferation and survival of malignant glioma cells, which suggests that inhibition of angiogenesis might be an effective therapeutic strategy. Anti-angiogenic therapies that target VEGF and the VEGF receptor (VEGFR) are effective adjuncts to the treatment of solid tumours. Normalisation of dilated and leaky tumour vasculature might also enable anti-angiogenic therapy to increase the efficacy of radiation therapy and cytotoxic chemotherapy. RECENT DEVELOPMENTS Several studies have investigated the use of bevacizumab--a humanised monoclonal antibody against VEGF--for patients with recurrent malignant glioma. Treatment with bevacizumab is commonly combined with cytotoxic chemotherapy and results in dramatic responses seen on radiographs, prolongation of progression-free survival, and less need for corticosteroids. Similar results have been shown with small-molecule inhibitors of VEGFR, such as cediranib. Anti-angiogenic treatment is generally well tolerated but common adverse effects include hypertension and proteinuria, whereas the potentially more serious adverse effects, such as thromboembolic disease and haemorrhage, occur infrequently. At least half of patients fail to respond to anti-angiogenic treatment and the response duration is variable. Resistance to anti-angiogenic therapy might implicate alternative pro-angiogenic factors, such as basic fibroblast growth factor, stromal-derived factor-1alpha, the angiopoietin receptor Tie2, and placental growth factor. Anti-angiogenic therapy might also lead to mobilisation of circulating endothelial cells towards the tumour, which supports angiogenesis. Another possible mechanism of resistance of malignant glioma cells might be upregulation of pro-invasive molecules, which would result in increased infiltrative tumour growth along the blood vessels. WHERE NEXT?: Although anti-angiogenic therapies are promising, the duration of response with available regimens is modest. Continuing investigations will determine whether these drugs are best used for newly diagnosed or recurrent tumours and will establish the optimum combinations with radiation, cytotoxic chemotherapy, and other targeted molecular compounds. As yet, there are no effective treatments for patients on anti-angiogenic therapies whose tumours progress. Further understanding of the mechanisms of resistance to anti-angiogenic therapies and better selection of patients will be crucial to improve outcomes for patients with malignant glioma.

Role of a second chemotherapy in recurrent malignant glioma patients who progress on bevacizumab

Bevacizumab is a humanized monoclonal antibody against vascular endothelial growth factor (VEGF) that has efficacy in recurrent malignant gliomas, particularly in combination with irinotecan. However, responses are rarely durable. Continuation of bevacizumab in combination with another chemotherapeutic agent may demonstrate some activity. In this article we present a retrospective review of 54 patients with recurrent malignant gliomas who progressed on a bevacizumab-containing regimen and were then treated with an alternate bevacizumab-containing regimen. All patients received intravenous bevacizumab (5-10 mg/kg) every 2 weeks alone or in combination with an additional chemotherapeutic agent, such as irinotecan. There was no limit on the number of prior therapies. Clinical characteristics and outcomes were reviewed. Tumor progression was determined by a combination of clinical status and radiographic changes. Patients were 33 men, 21 women (median age, 50 years; range, 23-72 years) with a median KPS score of 80 prior to the first bevacizumab-containing regimen and 70 prior to the second regimen; median prior chemotherapy regimens including the first bevacizumab-containing regimen was 3 (range, 2-5). Median progression-free survival (PFS) on the first bevacizumab-containing regimen was 124 days (95% confidence interval [CI], 87-154 days); 6-month (6M)-PFS was 33%. Median PFS on the second bevacizumab-containing regimen was 37.5 days (95% CI, 34-42 days); 6M-PFS was 2%. Ten patients on the first regimen and 12 patients on the second regimen suffered grade 3/4 toxicities. Those patients with malignant gliomas who progressed despite a bevacizumab-containing regimen rarely responded to the second bevacizumab-containing chemotherapeutic regimen. In such patients, alternate therapies should be considered.

Phase II Study of Protracted Daily Temozolomide for Low-Grade Gliomas in Adults

Purpose: Resistance to temozolomide chemotherapy is partly mediated by O6-methylguanine-DNA methlytransferase (MGMT). Protracted treatment with temozolomide potentially overcomes MGMT resistance and improves outcome. We conducted a phase II study of protracted daily temozolomide in adults with low-grade gliomas. Experimental Design: Patients with newly diagnosed oligodendroglioma or oligoastrocytoma with a MIB-1 index of >5% or recurrent low-grade gliomas received temozolomide (75 mg/m2/day in 11-week cycles of 7 weeks on/4 weeks off). Treatment continued for a total of six cycles or until tumor progression or unacceptable toxicity. Primary end point was best overall response rate; secondary end points were progression-free survival, overall survival, and toxicity. We correlated response with MGMT promoter methylation and chromosome 1p/19q deletion status. Results: Forty-four patients were treated (14 female, 30 male) with a median follow-up of 39.4 months. Median age was 43 years (range, 20-68 years) and median Karnofsky performance status was 90 (range, 70-100). The regimen was well tolerated. No patients had a complete response (0%), 9 had partial response (20%), 33 had stable disease (75%), and 2 had progressive disease (5%). A total of 21 patients eventually progressed with an overall median progression-free survival of 38 months. Patients with methylated MGMT promoter had a longer overall survival (P = 0.008). Deletion of either 1p or 19q chromosomes also predicted longer overall survival (hazard ratio, 0.17; 95% confidence interval, 0.03-0.93; log-rank P = 0.02). Conclusions: A protracted course of daily temozolomide is a well-tolerated regimen and seems to produce effective tumor control. This compares favorably with historical data on the standard 5-day temozolomide regimen.

Medical therapies for meningiomas

Meningiomas are the most common primary brain tumor in adults. Although the majority of these tumors can be effectively treated with surgery and radiation therapy, an important subset of patients have inoperable tumors, or develop recurrent disease after surgery and radiotherapy, and require some form of medical therapy. There are increasing numbers of studies evaluating various medical therapies but the results remain disappointing. Chemotherapies and hormonal therapies have been generally ineffective, although somatostatin analogues may have therapeutic potential. There is also increasing interest in targeted molecular therapies. Agents inhibiting platelet derived growth factor receptors and epidermal growth factor receptors have shown little efficacy, but molecular agents inhibiting vascular endothelial growth factor receptors appear to have some promise. As with other tumors, advances in the medical therapies for meningiomas will require improved understanding of the molecular pathogenesis of these tumors, more predictive preclinical models, and efficient mechanisms for conducting clinical trials, given the small population of eligible patients.

Phase II study of imatinib mesylate for recurrent meningiomas (North American Brain Tumor Consortium study 01-08)

Platelet-derived growth factor (PDGF) and its receptors (PDGFR) are frequently coexpressed in meningiomas, potentially contributing to their pathogenesis. The North American Brain Tumor Consortium conducted a phase II study to evaluate the therapeutic potential of imatinib mesylate (Gleevec), a PDGFR inhibitor, in patients with recurrent meningiomas. Patients were stratified into benign (WHO grade I) meningiomas or atypical (WHO grade II) and malignant (WHO grade III) meningiomas. The primary end point was 6-month progression-free survival (6M-PFS). Patients requiring enzyme-inducing antiepileptic drugs were ineligible. Patients received imatinib at a dose of 600 mg/day for the first 4-week cycle and then gradually increased to 800 mg/day for subsequent cycles, if there were no unacceptable toxicities. Plasma concentrations of imatinib and its active metabolite, CGP74588, were assessed. Twenty-three heavily pretreated patients were enrolled into the study (13 benign, 5 atypical, and 5 malignant meningiomas), of whom 22 were eligible. The study was closed prematurely due to slow accrual. Tissue was available only from a minority of patients, but in these specimens there was uniform distribution of PDGFR, the drug target. Imatinib was generally well tolerated. Of 19 patients evaluable for response, 10 progressed at the first scan, and 9 were stable. There were no complete or partial responses. Overall median PFS was 2 months (range, 0.7-34 months); 6M-PFS was 29.4%. For benign meningiomas, median PFS was 3 months (range, 1.1-34 months); 6M-PFS was 45%. For atypical and malignant meningiomas, median PFS was 2 months (range, 0.7-3.7 months); 6M-PFS was 0%. Cycle 1 trough concentrations of imatinib and CGP74588 were 2,129 +/- 1,600 ng/ml and 517 +/- 326 ng/ml, respectively. Single-agent imatinib was well tolerated but had no significant activity in recurrent meningiomas. Trough plasma concentrations of imatinib exceeded those associated with imatinib activity in chronic myelogenous leukemia.

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.

Phase II trial of sunitinib for recurrent and progressive atypical and anaplastic meningioma

BACKGROUND No proven effective medical therapy for surgery and radiation-refractory meningiomas exists. Sunitinib malate (SU011248) is a small-molecule tyrosine kinase inhibitor that targets vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor, abundant in meningiomas. METHODS This was a prospective, multicenter, investigator-initiated single-arm phase II trial. The primary cohort enrolled patients with surgery and radiation-refractory recurrent World Health Organization (WHO) grades II-III meningioma. An exploratory cohort enrolled patients with WHO grade I meningioma, hemangiopericytoma, or hemangioblastoma. Sunitinib was administered at 50 mg/d for days 1-28 of every 42-day cycle. The primary endpoint was the rate of 6-month progression-free survival (PFS6), with secondary endpoints of radiographic response rate, safety, PFS, and overall survival. Exploratory objectives include analysis of tumoral molecular markers and MR perfusion imaging. RESULTS Thirty-six patients with high-grade meningioma (30 atypical and 6 anaplastic) were enrolled. Patients were heavily pretreated (median number of 5 recurrences, range 2-10). PFS6 rate was 42%, meeting the primary endpoint. Median PFS was 5.2 months (95% CI: 2.8-8.3 mo), and median overall survival was 24.6 months (95% CI: 16.5-38.4 mo). Thirteen patients enrolled in the exploratory cohort. Overall toxicity included 1 grade 5 intratumoral hemorrhage, 2 grade 3 and 1 grade 4 CNS/intratumoral hemorrhages, 1 grade 3 and 1 grade 4 thrombotic microangiopathy, and 1 grade 3 gastrointestinal perforation. Expression of VEGFR2 predicted PFS of a median of 1.4 months in VEGFR2-negative patients versus 6.4 months in VEGFR2-positive patients (P = .005). CONCLUSION Sunitinib is active in recurrent atypical/malignant meningioma patients. A randomized trial should be performed.