Risk and management of venous thromboembolisms in bevacizumab-treated metastatic colorectal cancer patients

Bevacizumab may potentiate the risk of venous thromboembolisms (VTEs) in cancer patients, who are already predisposed to pro-thrombotic states. We aimed to characterize the incidence of VTEs in a population-based cohort of metastatic colorectal cancer (mCRC) patients treated with bevacizumab, describe patient and treatment factors associated with VTEs, and examine how VTEs are managed.

Patients diagnosed with mCRC from 2006 to 2009 and offered bevacizumab were included. Descriptive statistics were used to describe VTE occurrences and management. Univariate and multivariate regression models were constructed to explore associations between clinical factors and VTEs.

We identified 541 mCRC patients: 27 never started bevacizumab and 15 were lost to follow-up. Of the 499 evaluable patients, median age was 61, 59.3 % were men, 88.1 % had ECOG 0/1, and 5.2 % reported previous VTEs. Mean number of bevacizumab doses was 13.3 cycles. After receiving bevacizumab, 81 patients developed 93 cases of VTEs, with 9 patients experiencing >1 event. Individuals who experienced VTEs were more likely to have had pre-existing cardiovascular disease (OR 2.259, p = 0.0245), resection of primary cancer (OR 3.262, p = 0.0269), pre-chemotherapy platelet count ≥350,000/μL (OR 2.295, p = 0.0293), and received >12 bevacizumab cycles (OR 2.172, p = 0.0158). Use of bevacizumab varied after occurrence of VTE where it was discontinued in 34.4 %, continued in 34.4 %, and temporarily held in 1.1 %.

VTE risk can be high, especially in patients with specific pre-treatment risk factors as well as in those who received more bevacizumab, suggesting a potential dose-related effect. Management of bevacizumab-related VTEs was variable.