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Tuesday, December 4, 2007

Avastin for Breast Cancer awaits FDA Panel Review

The US Food and Drug Administration (FDA) Oncology Drug Advisory Committee is to meet tomorrow, Wednesday 5th December, to decide whether to recommend the agency approve Genentech Inc's cancer drug Avastin as a treatment for breast cancer. The FDA does not have to follow the advice of its advisory panels, which include practicing physicians, but it usually does.

The panel will review two papers during the meeting. One paper is the drug company's application for approval supported by evidence from clinical trials. The other paper is a review of the clinical evidence by FDA staff.

Genentech want the FDA to extend its current approval to say that: "Avastin, in combination with paclitaxel, is indicated for the treatment of patients who have not received chemotherapy for their locally recurrent or metastatic breast cancer."

The drug company's papers show evidence of significantly improved progression free survival rates (PFS) among clinical trial participants. In a study involving some 700 patients, the median PFS went up by 5.5 months. PFS measures how long before the cancer gets worse.

The FDA staff's review acknowledges the improved PFS rates from the Genentech clinical trials, but said this must be weighed against no significant change in overall survival, and more serious side effects, including death.

Avastin (bevacizumab) is currently approved by the FDA for treating patients with colon and non-small cell lung cancer with other drugs, although some doctors have started using it "off label" to treat breast cancer.

Avastin is not a chemotherapy drug, it's a monoclonal antibody that starves cancer tumors by blocking the growth of blood vessels to the tumors. The disadvantage of chemotherapy drugs is that they can also kill healthy cells.

The FDA staff review drew attention to the fact that the grade 3 to grade 5 toxicity levels went up by 20.2 per cent when Avastin was added to paclitaxel. The rate of death in the Avastin and paclitaxel arm was 1.7 per cent higher than the paclitaxel only arm, and the serious side effects included: high blood pressure, blood clots, bowel perforation, and heart failure, as well as death.

Although the clinical evidence submitted by the drug company showed that patients on average survived 1.7 more months on Avastin than chemotherapy alone (26.5 versus 24.8 months), this figure was not statistically significant, said the FDA staff review.

Genentech concluded in their approval submission that:

"Analysis of the safety and efficacy data in total demonstrates a highly favorable risk-benefit profile for bevacizumab in combination with paclitaxel that supports full approval of bevacizumab for the treatment of locally recurrent and metastatic breast cancer."

The FDA staff review made no recommendation one way or the other, and commented that it was not always possible to tell whether it was the toxicity of the treatment or the tumor, or perhaps a combination of the two, that caused death.

Metastatic breast cancer patients usually die within 1.3 to 5 years of their diagnosis, said Genentech.

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