New studies show the medications can delay worsening of the advanced form of the illness.
Scientists attending the San Antonio Breast Cancer Symposium this week got the news about the medications.
One of the drugs was developed by Roche Holding.
In tests, it extended the time without tumor growth for more than six months when given with other drugs to treat breast cancer.
The other drug comes from Novartis.
It added more than four months to survival time without tumor growth when given with other breast cancer drugs.
The results of the studies about the drugs are published in the "New England Journal of Medicine."
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