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Bevacizumab not significantly associated with VTE risk in patients with prostate cancer
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Bevacizumab was significantly associated with an increased risk for arterial thromboembolism among patients with prostate cancer but was not significantly associated with risk for venous thromboembolism, according to study results.
Patients with cancer are approximately four times more likely to experience a thromboembolism than those without cancer. Prior research demonstrated that bevacizumab (Avastin, Genentech) is linked to increased risk for arterial thromboembolism (ATE), but its effect on VTE had not been established. Little data exist on the factors that increase the risk for ATE and VTE in patients with prostate cancer, according to study background.
Jai N. Patel
Jai N. Patel, PharmD, chief of pharmacology research at Levine Cancer Institute at Carolinas HealthCare System and a HemOnc Today Editorial Board member, and colleagues investigated the association of bevacizumab treatment and other clinical factors with risk for ATE and VTE.
“The main reasoning behind completing the study was essentially twofold,” Patel told HemOnc Today. “Given that the influence of bevacizumab on VTE is somewhat controversial, we wanted to examine the influence of bevacizumab treatment on the risk of VTE in a population of cancer patients (those with prostate cancer) who aren’t necessarily at a significantly higher risk of VTE compared with other tumor types. Secondly, we wanted to examine the influence of patient-specific parameters on ATE and VTE risk. The advantage of our study was the use of a time-to-event analysis, which was carried out under a competing risk model.”
The Cancer and Leukemia Group B 90401 trial included 1,008 men (median age, 69 years) with metastatic, castration-resistant prostate cancer. Approximately 68.2% were considered low risk on the validated VTE risk score, and 0.5% were considered high risk.
Researchers randomly assigned 503 patients to docetaxel, prednisone and bevacizumab once every 21 days. The other 505 men received docetaxel, prednisone and placebo.
The median duration of the therapies was eight cycles.
Of the total population, 26 patients experienced grade ≥3 ATE and 58 patients experienced grade ≥3 VTE.
Incidence of grade ≥3 ATE was 3.8% in the bevacizumab-treated group vs. 1.4% in the control group (OR=2.79; P=.02).
Univariate analysis of the VTE data demonstrated a trend toward decreased risk among patients who received bevacizumab. Incidence of the grade ≥3 VTE was 4.4% among bevacizumab-treated patients vs. 7.1% among those who received placebo (OR=0.6; P=.08). Those rates are lower than those reported in a previous pooled analysis (10.9% vs. 9.8%), but incidence of grade ≥3 VTE varies considerably based on tumor types and treatment regimens, Patel and colleagues wrote.
Patients assigned bevacizumab also demonstrated longer PFS, as well as higher rates of PSA response and objective response. However, they did not demonstrate longer OS.
Because VTE is a tumor-related complication, the trend toward decreased risk among patients assigned bevacizumab may be because of the drug’s trait of tumor control, researchers wrote.
Bevacizumab treatment and increasing age were statistically significant predictors of increased ATE risk, whereas there was a trend toward an increased risk in patients with prior ATE.
Alternatively, both increasing age and VTE risk score had statistically significant associations with increased risk for VTE.
Improved understanding of the factors that increase risk for ATE and VTE is necessary to minimize those risks and “reduce the burden of these prevalent complications in cancer care,” the researchers wrote.
“Many clinicians will either not take into account patient-specific risk factors or assume for certain risk factors to be true,” Patel said. “Although bevacizumab is not a standard treatment option for prostate cancer patients, these findings are still important, given that half of the patients in the analysis received standard docetaxel plus prednisone.” – by Anthony SanFilippo
Jai N. Patel, PharmD, can be reached at Levine Cancer Institute, Carolinas HealthCare System, 1021 Morehead Medical Drive, Charlotte, NC 28204; email: jai.patel@carolinashealthcare.org.
Disclosure: The researchers report grant funding from, employment relationships with, stock ownership in and consultant/advisory roles with AbbVie, Apotex, Astellas, Bayer, Biscayne Pharmaceuticals, Bristol-Myers Squibb, Cancer Genetics Inc., Cantex Pharmaceuticals, Cyclacel, Dicerna, Fresenius Kabi, Genentech, Janssen, Kinex Pharmaceuticals, Millennium, OncoTherapy Science, Onconova Therapeutics, PharmaMar, Sanofi-Aventis, Shionogi, Takeda, Teva, USV and Xspray.
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