UPDATE 1-Avastin slows progress of breast cancer in trial

(Adds comments from Genentech, oncologist and analyst, byline)

By Deena Beasley

CHICAGO, May 31 (Reuters) - The addition of Genentech Inc's DNA.N cancer drug Avastin to chemotherapy slows the progress of breast cancer at two different doses, according to results of a large international trial released on Saturday.

The trial showed that after 11 months, patients treated with a high dose of Avastin were 28 percent less likely to have their disease get worse compared with patients on chemotherapy alone. Those given a low dose of the drug were 21 percent less likely to have tumor growth compared to chemotherapy alone.

The results suggest that "the jury is still out" on whether a lower, and much less expensive, dose of Avastin would be an effective option for breast cancer patients, said Dr. Eric Winer, director of the oncology center at Dana-Faber Cancer Institute in Boston.

Dr. David Miles, of Mount Vernon Cancer Center in the United Kingdom and the study's lead investigator, said "the tendency is to think that the higher dose is best for our patients."

Avastin costs more than $4,000 a month at the low dose and double that for the high dose.

"The general message here is that Avastin has a role in breast cancer, but based on the scientific data it has not become the standard of care," Dr. Winer said.

Under U.S. Food and Drug Administration protocols -- which take into account differences in prognostic indicators and other changes -- the trial showed that progression-free survival was 39 percent better for patients on high-dose Avastin, and 31 percent better for the low-dose group, according to the researchers.