Updated from 5:08 p.m. EDT

Genentech

(DNA)

and

Roche

said a Phase III study of Avastin plus chemotherapy in first-line metastatic breast cancer met its primary endpoint of improving progression-free survival, compared with chemotherapy alone.

In a press release, the companies said the results from an interim analysis of the study showed that patients receiving Avastin and paclitaxel doubled the duration of surviving without cancer progression compared with the chemotherapy paclitaxel alone (or a hazard ratio of 0.50, which is equivalent to a 50% reduction in the risk of cancer progression).

Median progression-free survival was 11 months for patients treated with Avastin plus chemotherapy, vs. six months for patients treated with chemotherapy alone.

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At the interim analysis, a 49% improvement in the secondary endpoint of overall survival -- or a hazard ratio of 0.67, equaling a 33% reduction in the risk of death -- was observed.

In patients with measurable disease, the overall response rate was 28% in the Avastin plus chemotherapy arm, a 100% increase over the 14% observed in the chemotherapy alone arm. Avastin is currently approved for colon cancer.

The data were featured in a briefing at the annual meeting of the American Society of Clinical Oncology in Orlando, Fla.

This is the first time a drug that works by choking off the blood supply to tumors has been used to treat breast cancer, according to Kathy Miller, lead investigator of the study.

"The fact that Avastin has now demonstrated significant clinical benefits in three of the most common types of cancer

colon cancer, breast cancer and lung cancer highlights how this anti-angiogenesis drug has the potential to completely change the way we treat cancer, as it could become the mainstay of treatment for a whole range of cancers," Miller said.

Separately, Genentech said that data from an analysis of two Phase III studies of Herceptin in early-stage breast cancer showed that human epidermal growth factor receptor 2 (HER2)-positive breast cancer patients receiving Herceptin plus chemotherapy had a 52% reduction in the risk of disease recurrence compared with patients who received chemotherapy alone.

After four years in the study, 15% of women treated with Herceptin and chemotherapy experienced disease recurrence, vs. 33% of women treated with chemotherapy alone. Preliminary survival data showed a 49% improvement in overall survival, or a hazard ratio of 0.67, equivalent to a 33% reduction in the risk of death.