Using MRI techniques, we show here that normalization of tumor vessels in recurrent glioblastoma patients by daily administration of AZD2171-an oral tyrosine kinase inhibitor of VEGF receptors-has rapid onset, is prolonged but reversible, and has the significant clinical benefit of alleviating edema. Reversal of normalization began by 28 days, though some features persisted for as long as four months. Basic FGF, SDF1alpha, and viable circulating endothelial cells (CECs) increased when tumors escaped treatment, and circulating progenitor cells (CPCs) increased when tumors progressed after drug interruption. Our study provides insight into different mechanisms of action of this class of drugs in recurrent glioblastoma patients and suggests that the timing of combination therapy may be critical for optimizing activity against this tumor.

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.

A B S T R A C T PurposeGlioblastoma is an incurable solid tumor characterized by increased expression of vascular endothelial growth factor (VEGF). We performed a phase II study of cediranib in patients with recurrent glioblastoma. MethodsCediranib, an oral pan-VEGF receptor tyrosine kinase inhibitor, was administered (45 mg/d) until progression or unacceptable toxicity to patients with recurrent glioblastoma. The primary end point was the proportion of patients alive and progression free at 6 months (APF6). We performed magnetic resonance imaging (MRI) and plasma and urinary biomarker evaluations at multiple time points. ResultsThirty-one patients with recurrent glioblastoma were accrued. APF6 after cediranib was 25.8%. Radiographic partial responses were observed by MRI in 17 (56.7%) of 30 evaluable patients using three-dimensional measurements and in eight (27%) of 30 evaluable patients using twodimensional measurements. For the 15 patients who entered the study taking corticosteroids, the dose was reduced (n ϭ 10) or discontinued (n ϭ 5). Toxicities were manageable. Grade 3/4 toxicities included hypertension (four of 31; 12.9%); diarrhea (two of 31; 6.4%); and fatigue (six of 31; 19.4%). Fifteen (48.4%) of 31 patients required at least one dose reduction and 15 patients required temporary drug interruptions due to toxicity. Drug interruptions were not associated with outcome. Changes in plasma placental growth factor, basic fibroblast growth factor, matrix metalloproteinase (MMP) -2, soluble VEGF receptor 1, stromal cell-derived factor-1␣, and soluble Tek/Tie2 receptor and in urinary MMP-9/neutrophil gelatinase-associated lipocalin activity after cediranib were associated with radiographic response or survival. ConclusionCediranib monotherapy for recurrent glioblastoma is associated with encouraging proportions of radiographic response, 6-month progression-free survival, and a steroid-sparing effect with manageable toxicity. We identified early changes in circulating molecules as potential biomarkers of response to cediranib. The efficacy of cediranib and the predictive value of these candidate biomarkers will be explored in prospective trials.

Activation of the epidermal growth factor receptor (EGFR) in glioblastoma (GBM) occurs through mutations or deletions in the extracellular (EC) domain. Unlike lung cancers with EGFR kinase domain (KD) mutations, GBMs respond poorly to the EGFR inhibitor erlotinib. Using RNAi, we show that GBM cells carrying EGFR EC mutations display EGFR addiction. In contrast to KD mutants found in lung cancer, glioma-specific EGFR EC mutants are poorly inhibited by EGFR inhibitors that target the active kinase conformation (e.g., erlotinib). Inhibitors which bind to the inactive EGFR conformation, on the other hand, potently inhibit EGFR EC mutants and induce cell death in EGFR mutant GBM cells. Our results provide first evidence for single kinase addiction in GBM, and suggest that the disappointing clinical activity of first-generation EGFR inhibitors in GBM versus lung cancer may be attributed to the different conformational requirements of mutant EGFR in these two cancer types.

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.

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Sunitinib is active in recurrent atypical/malignant meningioma patients. A randomized trial should be performed.

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.