Etoposide with or without mannitol for the treatment of recurrent or primarily unresponsive brain tumors: a Children's Cancer Group Study, CCG-9881

The Normal and Brain Tumor Vasculature: Morphological and Functional Characteristics and Therapeutic Targeting

Glioblastoma is among the most common tumor of the central nervous system in adults. Overall survival has not significantly improved over the last decade, even with optimizing standard therapeutic care including extent of resection and radio- and chemotherapy. In this article, we review features of the brain vasculature found in healthy cerebral tissue and in glioblastoma. Brain vessels are of various sizes and composed of several vascular cell types. Non-vascular cells such as astrocytes or microglia also interact with the vasculature and play important roles. We also discuss in vitro engineered artificial blood vessels which may represent useful models for better understanding the tumor-vessel interaction. Finally, we summarize results from clinical trials with anti-angiogenic therapy alone or in combination, and discuss the value of these approaches for targeting glioblastoma.

Strategies for overcoming the blood-brain barrier for the treatment of brain metastases

The era of targeted therapy for cancer has been punctuated by some resounding successes, but with few exceptions, metastases to the brain remain frustratingly difficult to treat. It is increasingly apparent that old concerns regarding the ability of therapeutic agents to penetrate the blood-brain barrier have not been brushed aside by high-affinity small-molecule kinase inhibitors and monoclonal antibodies. Indeed, illustrative trends, such as the increasing incidence of brain metastases from HER2(+) breast cancer since the advent of trastuzumab therapy, have helped to solidify the concept of the CNS as a sanctuary site for cancer. With 200,000 patients diagnosed with brain metastases in the USA each year, the therapeutic challenge posed by the blood-brain barrier continues to be a big problem.

Phase 1 study of an oxaliplatin and etoposide regimen in pediatric patients with recurrent solid tumors

BACKGROUND

The combination of a platinating agent and etoposide has induced responses in various pediatric tumors. The study estimated the maximum tolerated dose (MTD) of an oxaliplatin and etoposide regimen in children with recurrent solid tumors.

METHODS

Oxaliplatin was administered on Day 1 and etoposide on Days 1 to 3 of each 21-day course. Cohorts of 3 to 6 patients were enrolled at 3 dose levels: 1) oxaliplatin at a dose of 130 mg/m(2) and etoposide at a dose of 75 mg/m(2), 2) oxaliplatin at a dose of 130 mg/m(2) and etoposide at a dose of 100 mg/m(2), and 3) oxaliplatin at a dose of 145 mg/m(2) and etoposide at a dose of 100 mg/m(2). Calcium and magnesium infusions were used at dose level 3 in an attempt to escalate the oxaliplatin dose past the single-agent MTD.

RESULTS

The 16 patients received a total of 63 courses. At dose level 1, dose-limiting epistaxis, neuropathy, and neutropenia occurred in 1 of 6 patients. No dose-limiting toxicity (DLT) occurred at dose level 2 (n = 6). At dose level 3, 2 of 4 patients experienced dose-limiting neutropenia; none experienced grade 3 or 4 acute neuropathy. Six patients required prolongation of the oxaliplatin infusion because of acute sensory neuropathy. Responses were observed in patients with medulloblastoma (1 complete response) and pineoblastoma (1 partial response); 3 others with atypical teratoid rhabdoid tumor, ependymoma, and soft tissue sarcoma had prolonged disease stabilization.

CONCLUSIONS

The MTD of this regimen was found to be oxaliplatin at a dose of 130 mg/m(2) given on Day 1 and etoposide at a dose of 100 mg/m(2)/d given on Days 1 to 3. Neutropenia was found to be the DLT. Calcium and magnesium infusions did not allow escalation of the oxaliplatin dose. The combination was well-tolerated and demonstrated antitumor activity.

Multiagent chemotherapy studied in a xenograft model of medulloblastoma/primitive neuroectodermal tumour: analysis of the VETOPEC regimen

Brain tumours remain the most important challenge in the treatment of childhood cancer. The intraocular (io) xenograft model was used to study components and variations of the VETOPEC multiagent chemotherapy regimen in the medulloblastoma/primitive neuroectodermal tumour (MB/PNET) xenograft cell line JRMB-6. VETOPEC, a combination of vincristine (VCR), etoposide (VP-16) and escalated dose cyclophosphamide (CPA), has been shown to be highly active in clinical trials. A total of 190 xenografted tumours were treated with one of nine regimens: saline; single agent CPA, VP-16 (single dose [sd], five dosages daily [dx5] or continuous infusion, [ci]) or VCR; combinations of CPA (dx5)+VP-16 (dx5 or ci) or CPA (dx5)+VP-16 (ci)+VCR (sd). Results were calculated using both response (volume reduction >50%) and 'time to progression' (TtP). Effectiveness of CPA was confirmed. Single-agent VCR or VP-16 produced no response. No difference was documented in TtP with VCR, VP-16 (sd) or VP-16 (dx5) versus control, but a significant prolongation occurred when VP-16 was given by ci (p=0.001). With the 3-agent combination of CPA+VP-16 (ci)+VCR a significantly prolonged TtP was documented versus both single agent CPA (p=0.003) and the combination of CPA+VP-16 (dx5) (p=0.004). The results suggest improved efficacy of VP-16 when given as ci in both single-agent and combination settings. The addition of VP-16 (ci)+VCR to an already effective dosage of CPA further prolongs TtP. These data support and progress VETOPEC phase II clinical studies and suggest potential further benefits of prolonged exposure to VP-16 by ci.

Pilot study of ifosfamide/carboplatin/etoposide (ICE) for peripheral blood stem cell mobilization in patients with high-risk or relapsed medulloblastoma

OBJECTIVES

The purpose of this study is to evaluate the stem cell mobilization capacity, anti-tumor effect, and feasibility of ifosfamide/carboplatin/etoposide (ICE) for transplant-eligible patients with medulloblastoma.

MATERIALS AND METHODS

Six patients (23 months to 18 years old) with high-risk or relapsed medulloblastoma received one cycle of ICE, which consisted of ifosfamide at 1.8 g/m(2) for 5 days, carboplatin 400 mg/m(2) for 2 days, and etoposide 100 mg/m(2) for 5 days. Stem cells were mobilized with ICE followed by granulocyte colony-stimulating factor at 10 microg kg(-1) day(-1).

RESULTS

After one cycle of ICE, the median number of harvested CD34+ cells per apheresis session was 11.85 x 10(6) cells/kg (range, 0.2 to 71.2 x 10(6) cells/kg). Two patients obtained a complete response and three patients a partial response. All patients experienced severe myelosuppression, and three infectious toxicities were observed.

CONCLUSIONS

These results suggest that ICE is optimal for mobilizing stem cells, effective for high-risk or relapsed medulloblastoma, and tolerable with limited non-hematological toxicity.

Novel advances in drug delivery to brain cancer

The therapy of brain tumors has been limited by a lack of effective methods of drug delivery to the brain. Systemic administration is often associated with toxic side effects and ultimately fails to achieve therapeutic concentrations within a tumor. An attractive strategy that has gained importance in brain tumor therapy has relied on local and controlled delivery of chemotherapeutic agents by biodegradable polymers. This technique allows direct exposure of tumor cells to a therapeutic agent for a prolonged period of time and has been shown to prolong the survival of patients with malignant brain tumors. The use of polymers for local drug delivery greatly expands the spectrum of drugs available for the treatment of malignant brain tumors. This review discusses the rationale for local drug delivery, describes the development of currently available polymer-based therapeutic agents, and highlights examples of promising non-polymer based drug delivery methods for use in the treatment of malignant brain tumors.

The DNA damaging agent etoposide activates a cell survival pathway involving alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors and mitogen-activated protein kinases in hippocampal neurons

Etoposide, an inhibitor of topoisomerase II that induces DNA damage and can trigger cell death, is used as a chemotherapeutic agent. Because chemotherapies can result in neurological complications and because DNA damage in neurons is implicated in the pathogenesis of several neurodegenerative disorders, we studied the effects of etoposide on cultured hippocampal neurons. We found that etoposide induces neuronal apoptosis and that, prior to the cell death commitment point, there is an increase in whole-cell alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-induced current but no change in N-methyl-D-aspartate (NMDA)-induced current. Associated with the increase in AMPA-induced current was an increase in the amounts of AMPA receptor subunits GluR1 and GluR4, whereas levels of the NMDA receptor subunit NR1 were unaffected by etoposide. AMPA receptor activation can result in excitotoxic cell death but can also activate signaling pathways that promote synaptic plasticity and cell survival. We found that etoposide increases the activation of p42 and p44 mitogen-activated protein (MAP) kinases, and that activation of the MAP kinases by etoposide requires AMPA receptor activation. Pharmacological blockade of AMPA receptors and p42/p44 MAP kinases, but not of NMDA receptors, exacerbated etoposide-induced cell death. These findings suggest that, although etoposide is neurotoxic, it also activates a cell survival pathway involving AMPA receptor-mediated activation of p42/p44 MAP kinases. Agents that selectively inhibit the cell life or death pathways triggered by DNA damage may prove useful in the settings of cancer and neurodegenerative disorders, respectively.

Pharmacotherapy of malignant astrocytomas of children and adults: current strategies and future trends

This article reviews the conceptual progression in the pharmacological therapy of malignant astrocytoma (MA) over the past decade, and its future trends. It is a selective rather than an exhaustive inventory of literature citations. The experience of the Brain Tumour Cooperative Group (BTCG) and earlier phase III trials are summarised to place subsequent phase II and I studies of single and combination agent chemotherapy in perspective. The BTCG experience of the 1970s to 1980s may be summarised to indicate that external beam radiotherapy (EBRT) is therapeutic, although not curative, and not further improved upon by altering fractionation schedules, or the addition of radioenhancers. Whole brain and reduced whole brain EBRT with focal boost were comparable regimens. Nitrosourea-based, adjuvant chemotherapy provided a modest improvement in survival among adult patients, which was comparable with that of other single drugs or multidrug regimes. The multiagent schedules, however, had a correspondingly higher toxicity rate. Intra-arterial administration was associated with significant risk, which conferred no therapeutic advantage. The trend of the past decade has been towards multiagent chemotherapy although its benefit cannot be predicted from the classic prognostic factors. Published experience with investigational trials utilising myeloablative chemotherapy with autologous bone marrow or peripheral blood stem cell haemopoietic support, drug delivery enhancement methods and radiosensitisers is critically reviewed. None of these approaches have achieved wide-spread acceptance in the treatment of adult patients with MA. Greater attention is placed on recent 'chemoradiotherapy' trials, which attempt to integrate and maximise the cytoreductive potential of both modalities. This approach holds promise as an effective means to delay or overcome the evolution of tumour resistance, which is probably one of the dominant determinants of prognosis. However, the efficacy of this approach remains unproven. New chemotherapeutic agents as well as biological response modifiers, protein kinase inhibitors, angiogenesis inhibitors and gene therapy are also discussed; their role in the therapeutic armamentarium has not been defined.