Bevacizumab (Avastin; Genentech, Inc, South San Francisco, CA) is a recombinant monoclonal antibody against vascular endothelial growth factor (VEGF) that is used to treat metastatic cancers of the colon, rectum, kidney, and breast. Its side effects include proteinuria (35% of patients), hypertension (15%–30% of patients), gastrointestinal perforations (5%–7% of patients), and arterial emboli (0.5%–1% of patients)(1–3). Although these toxic effects are more frequent in patients with atherosclerosis, their pathophysiology remains unresolved.

We observed that patients treated with bevacizumab who developed hypertension had similar clinical presentations and biologic features, leading us to propose a unique mechanism for the vascular side effects of bevacizumab. From June to October 2005, we prospectively observed 22 consecutive patients (six renal cancer patients and 16 colorectal cancer patients) who were being treated with bevacizumab at the Cochin University Hospital (Paris, France). All patients were instructed how to assess their blood pressure according to the current guidelines (4) and were asked to do so twice daily. All characteristics of this patient population (Table 1) were similar to those of other populations of patients treated with bevacizumab in previously published trials (1, 2), except for performance status, which was 1 for most of our patients and 0 for patients in the previous studies.