Bevacizumab-related hypertension: Search for underlying mechanisms

Abstract

e14520 Background: Hypertension is a commonly observed side effect of inhibitors of VEGF/VEGFR-2 signaling such as bevacizumab. The mechanisms leading to this increase in blood pressure during anti-angiogenic therapy have not been elucidated. Recent studies suggest that functional rarefaction (a decrease in perfused microvessels) or anatomic rarefaction (a reduction in capillary density) may play an important role. The purpose of this study was to search for possible mechanisms that cause hypertension in patients treated with anti-angiogenic therapy and to confirm our hypothesis that systemic inhibition of VEGF inhibits vascular function and causes rarefaction. Methods: Patients treated with bevacizumab for any type of cancer were eligible. Measurements of blood pressure, flow-mediated dilatation (FMD), nitroglycerin-mediated dilatation (NMD), aortic pulse wave velocity (PWV), and capillary density and diameter with sidestream dark field (SDF) imaging of the mucosal microcirculation of the lip were performed at baseline, after 6 weeks of treatment, and 3 months after discontinuation of bevacizumab treatment. Results: Fourteen patients were included in this study. During bevacizumab treatment the mean systolic and diastolic blood pressure values increased, +3.4 mmHg (p=0.406), and +5.6 mmHg (p=0.023) resp. Mean FMD showed a statistically significant decrease of -3.1% (p=0.006). Mean NMD was unchanged. After 6 weeks treatment mean PWV increased significantly +0.7 m/s (p=0.0.027). A significant reduction in capillary density was seen from 18.0 capillary loops per image at baseline to 12.7 after 6 weeks (p=0.000007). Also a significant reduction in capillary diameter was seen, from 6.9 to 5.6 μm (p=0.002). Results after discontinuation of bevacizumab treatment were not yet available. Conclusions: Rarefaction (reduction in capillary density) and endothelial dysfunction observed in this study provide a plausible mechanism for the increase in blood pressure which results from treatment with bevacizumab. No significant financial relationships to disclose.