Jay S. Loeffler

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.

Lessons from phase III clinical trials on anti-VEGF therapy for cancer

In randomized phase III trials two anti-vascular endothelial growth factor (VEGF) approaches have yielded survival benefit in patients with metastatic cancer. In one approach, the addition of bevacizumab, a VEGF-specific antibody, to standard chemotherapy improved overall survival in colorectal and lung cancer patients and progression-free survival in breast cancer patients. In the second approach, multitargeted tyrosine kinase inhibitors that block VEGF receptor and other kinases in both endothelial and cancer cells, demonstrated survival benefit in gastrointestinal stromal tumor and renal-cell-carcinoma patients. By contrast, adding bevacizumab to chemotherapy failed to increase survival in patients with previously treated and refractory metastatic breast cancer. Furthermore, addition of vatalanib, a kinase inhibitor developed as a VEGF receptor-selective agent, to chemotherapy did not show a similar benefit in metastatic colorectal cancer patients. These contrasting responses raise critical questions about how these agents work and how to combine them optimally. We summarize three of the many potential mechanisms of action of anti-VEGF agents, and also discuss progress relating to the identification of potential biomarkers for anti-VEGF-agent efficacy in humans.

A multiinstitutional outcome and prognostic factor analysis of radiosurgery for resectable single brain metastasis

PURPOSE Recent randomized trials of selected patients with single brain metastasis comparing resection followed by whole-brain radiotherapy (WBRT) to WBRT alone have shown a statistically significant survival advantage for surgery and WBRT. A multiinstitutional retrospective study was performed, which identified comparable patients who were treated with stereotactic radiosurgery (RS) and WBRT. METHODS AND MATERIALS The RS databases of four institutions were reviewed to identify patients who met the following criteria: single-brain metastasis; no prior cranial surgery or WBRT; age > 18 years; surgically resectable lesion; Karnofsky Performance Status (KPS) > or = 70 at time of RS; nonradiosensitive histology. One hundred twenty-two patients were identified who met these criteria. Patients were categorized by: (a) status of the primary, (b) status of non-CNS metastasis, (c) age, (d) baseline KPS (from 70-100), (e) histology, (f) time from diagnosis of primary to the detection of the brain metastasis, (g) gender, and (h) tumor volume. RS was performed with a linear accelerator based technique (peripheral dose range was 10-27 Gy, median was 17 Gy). WBRT was performed in all but five patients who refused WBRT (dose range was 25-40 Gy, median was 37.5 Gy). RESULTS The median follow-up for all patients was 123 weeks. The overall local control rate (defined as lack of progression in the RS volume) was 86%. Intracranial recurrence outside of the RS volume was seen in 27 patients (22%). The actuarial median survival from date of RS is 56 weeks, and the 1-year and 2-year actuarial survival rates are 53% and 30%. The median duration of functional independence (sustained KPS > or = 70) is 44 weeks. Nineteen of 77 deaths were attributed to CNS progression (25% of all deaths). Multivariate analysis revealed the following factors to be statistically significant predictors of survival: baseline KPS (p < .0001) and absence of other sites of metastasis (p = 0.008). CONCLUSION The RS in conjunction with WBRT for single brain metastasis can produce substantial functional survival, especially in patients with good performance status and without extracranial metastasis. These results are comparable to recent randomized trials of resection and WBRT. The advantages of RS over surgery in terms of cost, hospitalization, morbidity, and wider applicability strongly suggest that a randomized trial to compare RS with surgery is warranted.

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.

Cellular-Telephone Use and Brain Tumors

BACKGROUND Concern has arisen that the use of hand-held cellular telephones might cause brain tumors. If such a risk does exist, the matter would be of considerable public health importance, given the rapid increase worldwide in the use of these devices. METHODS We examined the use of cellular telephones in a case-control study of intracranial tumors of the nervous system conducted between 1994 and 1998. We enrolled 782 patients through hospitals in Phoenix, Arizona; Boston; and Pittsburgh; 489 had histologically confirmed glioma, 197 had meningioma, and 96 had acoustic neuroma. The 799 controls were patients admitted to the same hospitals as the patients with brain tumors for a variety of nonmalignant conditions. RESULTS As compared with never, or very rarely, having used a cellular telephone, the relative risks associated with a cumulative use of a cellular telephone for more than 100 hours were 0.9 for glioma (95 percent confidence interval, 0.5 to 1.6), 0.7 for meningioma (95 percent confidence interval, 0.3 to 1.7), 1.4 for acoustic neuroma (95 percent confidence interval, 0.6 to 3.5), and 1.0 for all types of tumors combined (95 percent confidence interval, 0.6 to 1.5). There was no evidence that the risks were higher among persons who used cellular telephones for 60 or more minutes per day or regularly for five or more years. Tumors did not occur disproportionately often on the side of head on which the telephone was typically used. CONCLUSIONS These data do not support the hypothesis that the recent use of hand-held cellular telephones causes brain tumors, but they are not sufficient to evaluate the risks among long-term, heavy users and for potentially long induction periods.

Phase II Trial of the Antiangiogenic Agent Thalidomide in Patients With Recurrent High-Grade Gliomas

PURPOSE Little progress has been made in the treatment of adult high-grade gliomas over the last two decades, thus necessitating a search for novel therapeutic strategies. Malignant gliomas are vascular or angiogenic tumors, which leads to the supposition that angiogenesis inhibition may represent a potentially promising strategy in the treatment of these tumors. We present the results of a phase II trial of thalidomide, a putative inhibitor of angiogenesis, in the treatment of adults with previously irradiated, recurrent high-grade gliomas. PATIENTS AND METHODS Patients with a histologic diagnosis of anaplastic mixed glioma, anaplastic astrocytoma, or glioblastoma multiforme who had radiographic demonstration of tumor progression after standard external-beam radiotherapy with or without chemotherapy were eligible. Patients were initially treated with thalidomide 800 mg/d with increases in dose by 200 mg/d every 2 weeks until a final daily dose of 1,200 mg was achieved. Patients were evaluated every 8 weeks for response by both clinical and radiographic criteria. RESULTS A total of 39 patients were accrued, with 36 patients being assessable for both toxicity and response. Thalidomide was well tolerated, with constipation and sedation being the major toxicities. One patient developed a grade 2 peripheral neuropathy after treatment with thalidomide for nearly a year. There were two objective radiographic partial responses (6%), two minor responses (6%), and 12 patients with stable disease (33%). Eight patients were alive more than 1 year after starting thalidomide, although almost all with tumor progression. Changes in serum levels of basic fibroblastic growth factor (bFGF) were correlated with time to tumor progression and overall survival. CONCLUSION Thalidomide is a generally well-tolerated drug that may have antitumor activity in a minority of patients with recurrent high-grade gliomas. Future studies will better define the usefulness of thalidomide in newly diagnosed patients with malignant gliomas and in combination with radiotherapy and chemotherapy. Additionally, studies will be needed to confirm the potential utility of changes in serum bFGF as a marker of antiangiogenic activity and/or glioma growth.

Tolerance of cranial nerves of the cavernous sinus to radiosurgery

PURPOSE Stereotactic radiosurgery is becoming a more accepted treatment option for benign, deep seated intracranial lesions. However, little is known about the effects of large single fractions of radiation on cranial nerves. This study was undertaken to assess the effect of radiosurgery on the cranial nerves of the cavernous sinus. METHODS AND MATERIALS We examined the tolerance of cranial nerves (II-VI) following radiosurgery for 62 patients (42/62 with meningiomas) treated for lesions within or near the cavernous sinus. Twenty-nine patients were treated with a modified 6 MV linear accelerator (Joint Center for Radiation Therapy) and 33 were treated with the Gamma Knife (University of Pittsburgh). Three-dimensional treatment plans were retrospectively reviewed and maximum doses were calculated for the cavernous sinus and the optic nerve and chiasm. RESULTS Median follow-up was 19 months (range 3-49). New cranial neuropathies developed in 12 patients from 3-41 months following radiosurgery. Four of these complications involved injury to the optic system and 8 (3/8 transient) were the result of injury to the sensory or motor nerves of the cavernous sinus. There was no clear relationship between the maximum dose to the cavernous sinus and the development of complications for cranial nerves III-VI over the dose range used (1000-4000 cGy). For the optic apparatus, there was a significantly increased incidence of complications with dose. Four of 17 patients (24%) receiving greater than 800 cGy to any part of the optic apparatus developed visual complications compared with 0/35 who received less than 800 cGy (p = 0.009). CONCLUSION Radiosurgery using tumor-controlling doses of up to 4000 cGy appears to be a relatively safe technique in treating lesions within or near the sensory and motor nerves (III-VI) of the cavernous sinus. The dose to the optic apparatus should be limited to under 800 cGy.

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.

Charged particles in radiation oncology

Radiotherapy is one of the most common and effective therapies for cancer. Generally, patients are treated with X-rays produced by electron accelerators. Many years ago, researchers proposed that high-energy charged particles could be used for this purpose, owing to their physical and radiobiological advantages compared with X-rays. Particle therapy is an emerging technique in radiotherapy. Protons and carbon ions have been used for treating many different solid cancers, and several new centers with large accelerators are under construction. Debate continues on the cost:benefit ratio of this technique, that is, on whether the high costs of accelerators and beam delivery in particle therapy are justified by a clear clinical advantage. This Review considers the present clinical results in the field, and identifies and discusses the research questions that have resulted with this technique.

The Prognostic Significance of Phosphatidylinositol 3-Kinase Pathway Activation in Human Gliomas

PURPOSE The objectives of this study were to examine activation patterns of the phosphatidylinositol 3-kinase (PI3K) pathway in gliomas and to examine the prognostic significance of PI3K pathway activation using snap-frozen clinical specimens. MATERIALS AND METHODS Levels of expression of PI3K pathway members were assessed in 92 prospectively collected gliomas through quantitative Western analysis using total and phospho-specific antibodies for PI3K, Akt, and p70(s6k). Both expression and expression levels of these PI3K pathway members were correlated with histology, markers of apoptosis (cleaved caspase 3), and with clinical outcome (eg, overall survival). RESULTS It was determined that activation of all three PI3K pathway members were significantly more frequent in glioblastoma multiforme than in non-glioblastoma multiforme tumors. Levels of phospho-PI3K, phospho-Akt, and phospho-p70(s6k) were all found to be inversely associated with cleaved caspase 3 levels, suggesting PI3K pathway activation is associated with reduced levels of apoptosis. Perhaps most importantly, activation of PI3K pathway members was found to be significantly associated with reduced survival times when all glioma cases were considered in aggregate. When glioblastoma cases were considered separately, the prognostic value of PI3K activation remained significant, suggesting that PI3K activation may directly be associated with radiation resistance, given that this was the only adjuvant therapy administered to this subset of patients. CONCLUSION Activation of the PI3K pathway is significantly associated with increasing tumor grade, decreased levels of apoptosis, and with adverse clinical outcome in human gliomas. Molecular pathways regulating PI3K activation would appear to be promising targets in the clinical management of glioma patients.