Principal investigator Kathy D. Miller, MD, associate professor of hematology and oncology, Indiana University, Indianapolis, Indiana, presented her findings to a standing room only audience of several thousand at a late-breaking session.

Bevacizumab is a monoclonal antibody currently used for the treatment of colorectal cancer. It works by preventing the formation of new blood vessels (angiogenesis).

The drug has been shown to inhibit vascular endothelial growth factor (VEGF) activity. Previous research showed positive findings in other solid tumors that had metastasized. VEGF has also been shown to play a role in breast cancer.

Dr. Miller and colleagues in the Eastern Cooperative Oncology Group (ECOG) and the Breast Cancer Intergroup (BCIG) therefore designed their study to assess the efficacy of bevacizumab in breast cancer.

In Trial E2100 -- a randomized, phase 3 study -- the researchers compared the efficacy of bevacizumab added to weekly paclitaxel and weekly paclitaxel monotherapy.

The paclitaxel dose was 90 mg/m² given on days 1, 8, and 15 of a 28-day cycle. Patients in the bevacizumab arm also received a dose of 10 mg/m² on days 1 and 15 of each cycle.

Patients were a median of 55 years old. Approximately 40% of patients had progressed within 2 years, and approximately 25% had evidence of 3 or more metastases.

"The addition of bevacizumab to paclitaxel clearly improved the response rates, from 14.2% to 28.2%," she said. "It significantly improved the progression-free survival from 6.1 months to nearly 11 months, with a hazard ratio of 0.498, which is highly significant." When the investigators analyzed the overall survival data, they found that the combination therapy had a hazard ratio of 0.67.

The adverse events were consistent with those known for both drugs, she said. For example, approximately 13% of bevacizumab-treated patients developed hypertension that required treatment, and approximately 2.5% developed proteinuria of 2 g or more per day. Grade 3 neuropathy occurred in 13.6% of monotherapy patients and 19.9% of those in the bevacizumab arm.

The investigators concluded that the addition of bevacizumab improved response rates and prolonged progression-free survival rates, with minimal increases in toxicity.

Dr. Miller added that in ongoing studies, she and her colleagues will be investigating the treatment's impact on quality of life and biochemical markers of progression. She stressed that it will be necessary to follow this patient cohort longer to confirm bevacizumab's impact on overall survival.


[Presentation title: Monoclonal Antibodies in the Treatment of Breast Cancer. Late-breaking session]

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