Cyclophosphamide, Topotecan, and Bevacizumab (CTB) in Patients With Relapsed/Refractory Ewing's Sarcoma and Neuroblastoma

The purpose of this study is to find out what effects, good and/or bad treatment with a new combination of drugs, cyclophosphamide, topotecan, and bevacizumab has on the patient and their cancer. The medications, cyclophosphamide and topotecan, are standard drugs often used together for the treatment of cancer in children with either Ewing's sarcoma or neuroblastoma. Bevacizumab is an experimental drug called an antibody that targets a protein important in the growth of cancer cells called vascular endothelial growth factor (VEGF). VEGF is made by tumor and other surrounding cells to help make blood vessels needed for the growth and spread of cancer cells in the body. The way that bevacizumab works is to stop the cancer cells from making their own blood supply, causing the tumor to stop growing bigger or from spreading. In adult clinical trials, bevacizumab has shown promising anti-cancer activity in patients with cancer of the colon/rectum (colorectal) and breast. It has been approved by the Food and Drug Administration (FDA) for use in patients with colorectal cancer but not in cancers found in children. Bevacizumab has been tested in early clinical studies in children and has been shown to be safe. Other goals of this study will include research tests designed to test the following changes in the patient or their cancer: to see how the body handles and breaks down bevacizumab (pharmacokinetics), to look at changes in proteins in the blood that may affect the way the cancer responds to the combination (angiogenic profile, angiogenesis associated serum biomarkers), to look at changes in genes that may affect how the cancer responds to treatment with this combination of medications (metabolic signature), and to monitor the effects of changes in the way the body grows and develops before and after bevacizumab is given.