Is bevacizumab (Avastin) use in patients with metastatic colorectal cancer (mCRC) or non-small cell lung cancer (NSCLC) related to a higher incidence of thromboembolic events?

Clinical trials performed with bevacizumab demonstrated that the incidence of grade 3-4 venous thromboembolic events in patients with metastatic colorectal cancer (mCRC) or non-small cell lung cancer (NSCLC) is higher in those who receive bevacizumab in combination with chemotherapy than in those who receive chemotherapy alone (Avastin [package insert]; Nat Biotechnol. 2004;22[10]:1198.)

There was also evidence of an increased risk of developing a second subsequent thromboembolic event in patients with mCRC receiving bevacizumab and chemotherapy compared with those receiving chemotherapy alone. One study of 53 patients (14%) on bolus-intravenous fluorouracil (IFL) plus bevacizumab arm and 30 patients (8%) on the bolus-IFL plus placebo arm received full dose warfarin following a venous thromboembolic event. Of these patients studied, a secondary embolic event occurred in 21% (11/53) of patients receiving bolus-IFL plus bevacizumab and 3% (1/30) of patients receiving bolus-IFL alone. Whether possible drug-related inflammation leading to embolic disease is limited to patients with colorectal cancer who are receiving 5-fluorouracil-based therapy is still under investigation.

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As many as 5% of all patients using bevacizumab are at increased risk of thromboembolic events; however, the increased risk does not impact the basic risk/benefit ratio of the drug. The proactive approach for use of bevacizumab must be a balance between risk factors and benefit, and clinicians should be mindful that this risk does exist in patients who already have a heightened risk of thromboembolic events as a result of malignancy alone. — Jiajoyce R. Conway, DNP, FNP-BC, NP-C