BEVACIZUMAB. The mechanism associated with bevacizumabinduced
arterial thrombosis is unclear. It is thought, however,
that VEGF may be involved. VEGF stimulates endothelial cell
proliferation, promotes endothelial cell survival, and helps
maintain vascular integrity (99). Therefore, anti-VEGF therapy
may decrease the regenerative capability of endothelial cells
in response to trauma, leading to endothelial cell dysfunction
and defects in the interior vascular lining exposing subendothelial
collagen. As a result of subendothelial collagen exposure,
tissue factor is activated increasing the risk for thrombotic
events to occur (99,100). In addition, inhibiting VEGF causes
reduction in nitric oxide and prostacyclin, as well as increases
hematocrit and blood viscosity via overproduction of erythropoietin,
all of which may predispose patients to an increased
risk of thromboembolic events