Bevacizumab (Avastin) slows cancer growth in patients newly diagnosed with advanced breast cancer

A large, international trial has shown that adding the targeted therapy bevacizumab (Avastin) to the chemotherapy drug docetaxel (Taxotere) slows disease progression in patients without prior chemotherapy for locally advanced or metastatic breast cancer. Bevacizumab targets the blood vessels that feed tumours and is known as an antiangiogenic drug.

Previous studies have shown that adding bevacizumab to paclitaxel (Taxol, a taxane chemotherapy agent similar to docetaxel) for patients with metastatic breast cancer doubles progression-free survival. This is the first phase III trial to evaluate bevacizumab in combination with docetaxel, a drug that is used much more commonly in Europe, Asia, and Australia, while paclitaxel is used more often in the United States.

In February, the U.S. Food and Drug Administration approved bevacizumab in combination with paclitaxel for the treatment of newly diagnosed metastatic breast cancer; the drug was previously approved to treat colorectal cancer.

"This study shows the antiangiogenic approach to treating breast cancer is effective, regardless of which taxane drug it is combined with," said David Miles, MD, a professor and medical oncologist at the Mount Vernon Cancer Centre and the study's lead author. "We found it does not add a great deal to the toxicity of chemotherapy, which should be reassuring to physicians recommending this course of treatment."

In the current study, the AVADO trial, 736 patients were randomized among three arms: placebo plus docetaxel, a higher dose of bevacizumab (15 mg/kg) plus docetaxel, and a lower dose of bevacizumab (7.5 mg/kg) plus docetaxel. The higher dose was the standard that was established in earlier breast cancer studies; the lower dose was the standard used to treat colorectal cancer. After a median follow-up of 11 months, investigators found that patients in the low-dose group were 21 percent less likely to have their disease progress, compared with those who received docetaxel alone.

Patients in the high-dose group were 28 percent less likely to have their disease progress compared with those who received docetaxel only. The percentage of patients who had their tumors shrink was 44.4 percent in the placebo plus docetaxel group, 55.2 percent in the low-dose bevacizumab group, and 63.1 percent in the high-dose group. Because of the number of patients in the trial, it was not possible to statistically compare the two doses with each other.

Patients in the two bevacizumab groups had a slightly higher rate of severe side effects: 74.8 percent in the low-dose group and 74.1 percent in the high-dose group, compared with 67.0 percent in the docetaxelalone group. The most common side effect attributed to bevacizumab was high blood pressure, which was treatable with medication. Severe bowel perforation, a toxicity seen in some other bevacizumab trials, occurred in few patients: two patients in the placebo arm, and one patient in each of the experimental arms.