Antiangiogenic (metronomic) chemotherapy for brain tumors: current and future perspectives

Moving forward with metronomic chemotherapy: meeting report of the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology

Metronomic chemotherapy, which is defined by the frequent, repetitive administration of chemotherapeutic drugs at relatively low doses, and without prolonged drug-free break, is an emerging strategy to fight cancer. Initially thought to act by targeting tumor angiogenesis, additional mechanisms have been recently unveiled, and metronomic chemotherapy is now considered to represent a form of multitargeted therapy. Despite representing a genuine alternative for advanced and/or high-risk cancer therapy, the development of metronomic approaches in pediatric oncology is still in the early stage. The few numbers of large-scale state-of-the-art clinical trials, issues regarding terminology and the limited understanding of the complex and intertwined mechanisms of action of metronomic treatments have limited progress in this important field of research. On March 18 and 19, 2010, the 2nd International Workshop on Metronomic and Anti-Angiogenic Chemotherapy in Paediatric Oncology was held in Marseille, France, and brought together clinicians, basic scientists, physician-scientists, trainees, and students from all around the world. The main aim of this international meeting was to provide a unique forum to 1) reflect on the major advances that have been made in this field of research since its creation, 2) communicate results from the most recent clinical trials and preclinical studies, 3) discuss the current and future challenges of the field, and 4) set forth a solid framework for future collaborative biologic and clinical studies. The present report documents the main preclinical and clinical data that were presented in the keynote and best abstract sessions and delivers the key messages from the meeting.

Treatment of recurrent central nervous system primitive neuroectodermal tumours in children and adolescents: results of a Children's Cancer and Leukaemia Group study

BACKGROUND

The treatment of previously irradiated patients with recurrent central nervous system primitive neuroectodermal tumours (PNETs) is a considerable challenge. A study was undertaken to attempt to improve the outcome for such patients using a high dose chemotherapy (HDCT) based strategy.

METHODS

Between 2000 and 2007, 40 patients with relapsed medulloblastoma (MB) and 5 with relapsed supratentorial PNETs (StPNETs) were accrued. All but one had received prior craniospinal radiotherapy. Patients were initially treated with cyclophosphamide (4 g/m(2)) together with surgery or local radiotherapy where appropriate. If complete or near complete remission was achieved, the patient proceeded to receive two sequential courses of HDCT with stem cell rescue. The first course consisted of thiotepa (900 mg/m(2)) and the second carboplatin (AUC 21).

RESULTS

All five patients with StPNET died of tumour progression with a median OS of 0.4 years. Nineteen of the 40 patients with relapsed MB underwent surgery. Radiotherapy was administered to eight patients. All patients received at least one course of cyclophosphamide. Only 22 MB patients progressed to the HDCT phase; 10 patients received thiotepa only and 12 thiotepa and carboplatin. At a median follow-up of 7.4 years (Range 2.8-8.2 years), only three MB patients are still alive, one following a further relapse. Three and 5 year OS was 22.0% and 8.2%, respectively and 3 and 5 year EFS was 14.6% and 8.7%, respectively.

CONCLUSION

This national study based on a strategy including a particular tandem HDCT regimen showed no benefit for previously irradiated patients with relapsed StPNET and very limited benefit for patients with relapsed medulloblastoma.

New anti-angiogenic strategies in pediatric solid malignancies: agents and biomarkers of a near future

IMPORTANCE OF THE FIELD

Antiangiogenic strategies are affording considerable interest and have become a major milestone in therapeutics of various adult cancers. However, progress has been slow to expand such therapies to patients with pediatric solid malignancies.

AREAS COVERED IN THIS REVIEW

This review discusses the principal pathways for angiogenesis in pediatric solid malignancies and summarizes recent preclinical and clinical data on antiangiogenesis strategies in these tumors.

WHAT THE READER WILL GAIN

The reader will gain state-of-the-art knowledge in the current advancements of antiangiogenic therapies in pediatric clinical trials in regard to supporting preclinical data, and in the status of potential biomarkers investigated for monitoring angiogenesis inhibitors. Mechanisms of resistance to antiangiogenic therapy will also be discussed. Finally, we describe our experience in the monitoring of circulating endothelial cells and progenitors and their potential role as biomarkers of metastatic disease and resistance to antiangiogenic therapies.

TAKE HOME MESSAGE

Evaluation and development of antiangiogenesis protocols are starting and represent a crucial step in the management of pediatric solid malignancies today. Emphasis should be placed on the development of proper surrogate markers to monitor antiangiogenic activity and on the possible long-term effects of these therapies in a pediatric population.

Metabolic management of brain cancer

Malignant brain tumors are a significant health problem in children and adults. Conventional therapeutic approaches have been largely unsuccessful in providing long-term management. As primarily a metabolic disease, malignant brain cancer can be managed through changes in metabolic environment. In contrast to normal neurons and glia, which readily transition to ketone bodies (β-hydroxybutyrate) for energy under reduced glucose, malignant brain tumors are strongly dependent on glycolysis for energy. The transition from glucose to ketone bodies as a major energy source is an evolutionary conserved adaptation to food deprivation that permits the survival of normal cells during extreme shifts in nutritional environment. Only those cells with a flexible genome and normal mitochondria can effectively transition from one energy state to another. Mutations restrict genomic and metabolic flexibility thus making tumor cells more vulnerable to energy stress than normal cells. We propose an alternative approach to brain cancer management that exploits the metabolic flexibility of normal cells at the expense of the genetically defective and metabolically challenged tumor cells. This approach to brain cancer management is supported from recent studies in mice and humans treated with calorie restriction and the ketogenic diet. Issues of implementation and use protocols are presented for the metabolic management of brain cancer.

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.