Avastin May Help Fight Early Breast Cancer
Studies May Reopen Discussions About Benefits of Avastin for Breast Cancer
Testing Avastin for Early-Stage Breast Cancers continued...
That’s where the similarities ended.
When the German researchers took at closer look at their results, they were surprised to find that women whose cancers were not spurred by hormones -- so called triple-negative tumors -- were seeing larger-than-average benefits from Avastin.
Triple-negative tumors account for only about 10% to 20% of breast cancer, but they are among the toughest to treat. Studies have shown they are more likely to spread and recur than tumors that are sensitive to hormones.
Among women with triple-negative tumors, the rates of complete response were 27.9% for women on standard chemotherapy and 39.3% in those who also got Avastin.
In contrast, women with cancer that was sensitive to hormones had about the same results whether or not they got Avastin. “We didn’t really expect that,” says researcher Gunter von Minckwitz, MD, associate professor of gynecology at the University of Frankfurt and chair of the German Breast Group. “Almost all the effect comes from this triple-negative group.”
He says there is some clinical data to suggest that tumors that don’t respond to hormones may rely more heavily than other kinds of cancers on the development of new blood vessels for growth.
Avastin shuts down the ability of tumors to grow new vessels, thus starving the cancer of its food supply.
When researchers in the U.S. took a similarly close look at their data, they found the opposite.
Avastin’s effects were more pronounced among women with breast cancer that was driven by either the hormones estrogen or progesterone. Among these women, 15% on traditional chemotherapy saw their tumors go away compared to 23% of the group that also got Avastin.
“It may indicate that [Avastin] has activity [in breast cancer], and that activity may be more profound in certain subsets of patients,” says researcher Harry Bear, MD, a surgical oncologist at Virginia Commonwealth University School of Medicine in Richmond.
Both studies were supported in part by Roche, the company that makes Avastin. Other financing for the research came from government grants and the manufacturers of the chemotherapy drugs that were tested.