Side effects of anti-angiogenic drugs

Anti-angiogenic drugs and in particular anti-vascular endothelial growth factor (VEGF) agents have entered the clinical armamentarium against cancer. New unexpected toxicities have emerged. The incidence and the severity of these toxicities have a great variability in the different studies. Among them, bleeding is one of the most severe and difficult to manage. Bevacizumab retains the highest frequency of bleeding complications, in particular epistaxis, hemoptysis and gastrointestinal bleeding. Although a higher incidence of severe hemorrhages has not been consistently demonstrated during the treatment with bevacizumab, mild bleeding episodes appear clearly increased in the experimental arm of most trials. Cases of severe pulmonary hemorrhage were reported in patients with lung cancer; these events occurred mainly intra-tumor and were significantly associated with squamous cell histology. Trials with other small-molecule tyrosine kinase inhibitors like sunitinib or sorafenib showed an overall lower rate of bleeding complications, but still significantly higher than the control arm in many cases. The mechanisms of bleeding induced by anti-VEGF agents are complex and not yet fully clarified: the main hypothesis is that VEGF could promote endothelial cell survival and integrity in the adult vasculature and its inhibition may decrease the renewal capacity of damaged endothelial cells. Management of bleeding in patients treated with anti-VEGF agents is a challenging task because this complication is at least in part inherent to the efficacy of the drug and because there is also an increased risk of thrombosis, both arterial and venous. So far, only few preliminary data are available on a strategy to prevent hemorrhage and thrombotic event.