Tracy T. Batchelor

Angiogenesis in brain tumours

Despite aggressive surgery, radiotherapy and chemotherapy, malignant gliomas remain uniformly fatal. To progress, these tumours stimulate the formation of new blood vessels through processes driven primarily by vascular endothelial growth factor (VEGF). However, the resulting vessels are structurally and functionally abnormal, and contribute to a hostile microenvironment (low oxygen tension and high interstitial fluid pressure) that selects for a more malignant phenotype with increased morbidity and mortality. Emerging preclinical and clinical data indicate that anti-VEGF therapies are potentially effective in glioblastoma — the most frequent primary brain tumour — and can transiently normalize tumour vessels. This creates a window of opportunity for optimally combining chemotherapeutics and radiation.

Biomarkers of response and resistance to antiangiogenic therapy

No validated biological markers (or biomarkers) currently exist for appropriately selecting patients with cancer for antiangiogenic therapy. Nor are there biomarkers identifying escape pathways that should be targeted after tumors develop resistance to a given antiangiogenic agent. A number of potential systemic, circulating, tissue and imaging biomarkers have emerged from recently completed phase I–III studies. Some of these are measured at baseline (for example VEGF polymorphisms), others are measured during treatment (such as hypertension, MRI-measured Ktrans, circulating angiogenic molecules or collagen IV), and all are mechanistically based. Some of these biomarkers might be pharmacodynamic (for example, increase in circulating VEGF, placental growth factor) while others have potential for predicting clinical benefit or identifying the escape pathways (for example, stromal-cell-derived factor 1α, interleukin-6). Most biomarkers are disease and/or agent specific and all of them need to be validated prospectively. We discuss the current challenges in establishing biomarkers of antiangiogenic therapy, define systemic, circulating, tissue and imaging biomarkers and their advantages and disadvantages, and comment on the future opportunities for validating biomarkers of antiangiogenic therapy.

Phase II Study of Cediranib, an Oral Pan–Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Inhibitor, in Patients With Recurrent Glioblastoma

PURPOSE Glioblastoma 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. METHODS Cediranib, 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. RESULTS Thirty-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 two-dimensional measurements. For the 15 patients who entered the study taking corticosteroids, the dose was reduced (n = 10) or discontinued (n = 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-1alpha, and soluble Tek/Tie2 receptor and in urinary MMP-9/neutrophil gelatinase-associated lipocalin activity after cediranib were associated with radiographic response or survival. CONCLUSION Cediranib 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.

Report of an International Workshop to Standardize Baseline Evaluation and Response Criteria for Primary CNS Lymphoma

Standardized guidelines for the baseline evaluation and response assessment of primary CNS lymphoma (PCNSL) are critical to ensure comparability among clinical trials for newly diagnosed patients. The relative rarity of this tumor precludes rapid completion of large-scale phase III trials and, therefore, our reliance on the results of well-designed phase II trials is critical. To formulate this recommendation, an international group of experts representing hematologic oncology, medical oncology, neuro-oncology, neurology, radiation oncology, neurosurgery, and ophthalmology met to review current standards of reporting and to formulate a consensus opinion regarding minimum baseline evaluation and common standards for assessing response to therapy. The response guidelines were based on the results of neuroimaging, corticosteroid use, ophthalmologic examination, and CSF cytology. A critical issue that requires additional study is the optimal method to assess the neurocognitive impact of therapy and address the quality of life of PCNSL survivors. We hope that these guidelines will improve communication among investigators and comparability among clinical trials in a way that will allow us to develop better therapies for patients.

Treatment of Primary CNS Lymphoma With Methotrexate and Deferred Radiotherapy: A Report of NABTT 96–07

PURPOSE A multicenter, phase II study of single-agent, intravenous methotrexate in newly diagnosed non-AIDS-related primary CNS lymphoma was conducted in the New Approaches to Brain Tumor Therapy (NABTT) CNS Consortium. METHODS Methotrexate (8 g/m(2)) was initially administered every 2 weeks. The primary end point was radiographic CR or PR, as defined by standard radiographic criteria, and secondary end points were survival and drug-related toxicity. RESULTS Twenty-five patients were enrolled with a mean age of 60 years and median Karnofsky Performance Score of 80. Three of 14 patients who underwent lumbar puncture had malignant cells on CSF cytopathology, and five of 25 patients had ocular involvement. Two patients could not be evaluated for the primary end point because of the absence of measurable disease in one and death before radiologic imaging in another. All patients have completed the treatment program or progressed. Among 23 patients, there were 12 CR (52%), five PR (22%), one (4%) with stable disease, and five progressions (22%) while on therapy. Seven patients died of tumor progression, and two died of other causes. Median progression-free survival was 12.8 months. Median overall survival for the entire group had not been reached at 22.8+ months. The toxicity of this regimen was modest, with no grade 3 or 4 toxicity in 13 of 25 patients, grade 3 toxicity in eight of 25 patients, and grade 4 toxicity in four of 25 patients after 287 cycles of chemotherapy. CONCLUSION These results indicate that high-dose methotrexate is associated with modest toxicity and a radiographic response proportion (74%) comparable to more toxic regimens.

Randomized Trial of a Slow-Release Versus a Standard Formulation of Cytarabine for the Intrathecal Treatment of Lymphomatous Meningitis

PURPOSE To evaluate the efficacy and safety of a slow-release formulation of cytarabine (DepoCyt; Chiron Corp, Emeryville, CA, and Skye Pharma, Inc, San Diego, CA) that maintains cytotoxic concentrations of cytarabine (ara-C) in the CSF of most patients for more than 14 days. PATIENTS AND METHODS Twenty-eight patients with lymphoma and a positive CSF cytology were randomized to receive DepoCyt 50 mg once every 2 weeks or free ara-C 50 mg twice a week for 1 month. Patients whose CSF cytology converted to negative and who did not have neurologic progression received an additional 3 months of consolidation therapy and then 4 months of maintenance therapy. All patients received dexamethasone 4 mg orally bid on days 1 through 5 of each 2-week cycle. RESULTS The response rate was 71% for DepoCyt and 15% for ara-C on an intent-to-treat basis (P =.006). All of the patients on the DepoCyt arm but only 53% of those on the ara-C arm were able to complete the planned 1-month induction therapy regimen. Time to neurologic progression and survival trend in favor of DepoCyt (median, 78.5 v 42 days and 99.5 v 63 days, respectively; P >.05). DepoCyt treatment was associated with an improved mean change in Karnofsky performance score at the end of induction (P =.041). The major adverse events on both arms were headache and arachnoiditis, which were often caused by the underlying disease. CONCLUSION DepoCyt injected once every 2 weeks produced a high response rate and a better quality of life as measured by Karnofsky score relative to that produced by free ara-C injected twice a week.

Primary CNS Lymphoma

Primary CNS lymphoma (PCNSL), an uncommon form of extranodal non-Hodgkins lymphoma (NHL), has increased in incidence during the last three decades and occurs in both immunocompromised and immunocompetent hosts. PCNSL in immunocompetent patients is associated with unique diagnostic, prognostic, and therapeutic issues, and the management of this malignancy is different from that of other forms of extranodal NHL. Characteristic imaging features should be suggestive of the diagnosis, avoidance of corticosteroids, if possible, and early neurosurgical consultation for stereotactic biopsy. Because PCNSL may involve the brain, CSF, and eyes, diagnostic evaluation should include assessment of all of these regions as well as screening for possible occult systemic disease. Resection provides no therapeutic benefit and should be reserved for the rare patient with neurologic deterioration due to brain herniation. Whole-brain radiation therapy (WBRT) alone is insufficient for durable tumor control and is associated with a high risk of neurotoxicity in patients older than age 60. Neurotoxicity typically is associated with significant cognitive, motor, and autonomic dysfunction, and has a negative impact on quality of life. Chemotherapy and WBRT together improve tumor response rates and survival compared with WBRT alone. Methotrexate-based multiagent chemotherapy without WBRT is associated with similar tumor response rates and survival compared with regimens that include WBRT, although controlled trials have not been performed. The risk of neurotoxicity is lower in patients treated with chemotherapy alone.

Phase III Randomized Trial Comparing the Efficacy of Cediranib As Monotherapy, and in Combination With Lomustine, Versus Lomustine Alone in Patients With Recurrent Glioblastoma

PURPOSE A randomized, phase III, placebo-controlled, partially blinded clinical trial (REGAL [Recent in in Glioblastoma Alone and With Lomustine]) was conducted to determine the efficacy of cediranib, an oral pan-vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor, either as monotherapy or in combination with lomustine versus lomustine in patients with recurrent glioblastoma. PATIENTS AND METHODS Patients (N = 325) with recurrent glioblastoma who previously received radiation and temozolomide were randomly assigned 2:2:1 to receive (1) cediranib (30 mg) monotherapy; (2) cediranib (20 mg) plus lomustine (110 mg/m(2)); (3) lomustine (110 mg/m(2)) plus a placebo. The primary end point was progression-free survival based on blinded, independent radiographic assessment of postcontrast T1-weighted and noncontrast T2-weighted magnetic resonance imaging (MRI) brain scans. RESULTS The primary end point of progression-free survival (PFS) was not significantly different for either cediranib alone (hazard ratio [HR] = 1.05; 95% CI, 0.74 to 1.50; two-sided P = .90) or cediranib in combination with lomustine (HR = 0.76; 95% CI, 0.53 to 1.08; two-sided P = .16) versus lomustine based on independent or local review of postcontrast T1-weighted MRI. CONCLUSION This study did not meet its primary end point of PFS prolongation with cediranib either as monotherapy or in combination with lomustine versus lomustine in patients with recurrent glioblastoma, although cediranib showed evidence of clinical activity on some secondary end points including time to deterioration in neurologic status and corticosteroid-sparing effects.

Edema Control by Cediranib, a Vascular Endothelial Growth Factor Receptor–Targeted Kinase Inhibitor, Prolongs Survival Despite Persistent Brain Tumor Growth in Mice

PURPOSE Recent clinical trials of antivascular endothelial growth factor (VEGF) agents for glioblastoma showed promising progression-free and overall survival rates. However, available clinical imaging does not separate antitumor effects from antipermeability effects of these agents. Thus although anti-VEGF agents may decrease tumor contrast-enhancement, vascularity, and edema, the mechanisms leading to improved survival in patients remain incompletely understood. Our goal was to determine whether alleviation of edema by anti-VEGF agents alone could increase survival in mice. METHODS We treated mice bearing three different orthotopic models of glioblastoma with a VEGF-targeted kinase inhibitor, cediranib. Using intravital microscopy, molecular techniques, and magnetic resonance imaging (MRI), we measured survival, tumor growth, edema, vascular morphology and function, cancer cell apoptosis and proliferation, and circulating angiogenic biomarkers. RESULTS We show by intravital microscopy that cediranib significantly decreased tumor vessel permeability and diameter. Moreover, cediranib treatment induced normalization of perivascular cell coverage and thinning of the basement membrane, as mirrored by an increase in plasma collagen IV. These rapid changes in tumor vascular morphology and function led to edema alleviation -- as measured by MRI and by dry/wet weight measurement of water content -- but did not affect tumor growth. By immunohistochemistry, we found a transient decrease in macrophage infiltration and significant but minor changes in tumor cell proliferation and apoptosis. Systemically, cediranib increased plasma VEGF and placenta growth factor levels, and the number of circulating CXCR4(+)CD45(+) cells. However, by controlling edema, cediranib significantly increased survival of mice in the face of persistent tumor growth. CONCLUSION Anti-VEGF agents may be able to improve survival of patients with glioblastoma, even without inhibiting tumor growth.

A Hypermutation Phenotype and Somatic MSH6 Mutations in Recurrent Human Malignant Gliomas after Alkylator Chemotherapy

Malignant gliomas have a very poor prognosis. The current standard of care for these cancers consists of extended adjuvant treatment with the alkylating agent temozolomide after surgical resection and radiotherapy. Although a statistically significant increase in survival has been reported with this regimen, nearly all gliomas recur and become insensitive to further treatment with this class of agents. We sequenced 500 kb of genomic DNA corresponding to the kinase domains of 518 protein kinases in each of nine gliomas. Large numbers of somatic mutations were observed in two gliomas recurrent after alkylating agent treatment. The pattern of mutations in these cases showed strong similarity to that induced by alkylating agents in experimental systems. Further investigation revealed inactivating somatic mutations of the mismatch repair gene MSH6 in each case. We propose that inactivating somatic mutations of MSH6 confer resistance to alkylating agents in gliomas in vivo and concurrently unleash accelerated mutagenesis in resistant clones as a consequence of continued exposure to alkylating agents in the presence of defective mismatch repair. The evidence therefore suggests that when MSH6 is inactivated in gliomas, alkylating agents convert from induction of tumor cell death to promotion of neoplastic progression. These observations highlight the potential of large scale sequencing for revealing and elucidating mutagenic processes operative in individual human cancers.