Based on preclinical data, a phase I/II program with bevacizumab was initiated. The initial phase I trial enrolled 25 patients in a dose-escalation fashion (0.1-10.0 mg/kg on days 0, 28, 35, and 42). No grade 3 or 4 toxicity was seen that was directly attributable to therapy. There were three episodes of tumor-related bleeding, including a hemorrhage in a previously undetected cerebral metastasis. Grade 1 and 2 toxicities, possibly or probably related to treatment, included asthenia, headache, and nausea. There were no complete or partial responses seen, although one patient with renal cell carcinoma achieved a mixed response.