 Participants will receive bevacizumab intravenously by vein once a week for 2 weeks and then every 3 weeks at the National Institutes of Health NIH Clinical Center. The first infusion takes about 90 minutes, the second takes about 60 minutes, and subsequent infusions take about 30 minutes. Infusions may take longer, however, if the drug is better tolerated at a slower infusion rate. Patients will be evaluated with the following tests and procedures: 