Why Two Breast Cancer Drugs Don't Help Survival

Two breast cancer drugs, Avastin and Sutent, do not contribute to survival in breast cancer patients. The reason why is that they have been found to increase the number of cancer stem cells in breast tumors. This is according to research published in the Proceedings of the National Academy of Sciences.

Although Sutent and Avastin do shrink breast cancer tumors and slow the rate at which cancer develops, their effects have only a short-term benefit. The cancer eventually returns with a vengeance, growing and spreading to other organs.

Study author Max Wicha, M.D. wrote, "This study provides an explanation for the clinical trial results demonstrating that in women with breast cancer antiangiogenic agents such as Avastin delay the time to tumor recurrence but do not affect patient survival. If our results apply to the clinic, it suggests that in order to be effective, these agents will need to be combined with cancer stem cell inhibitors, an approach now being explored in the laboratory."

The research team conducted their study by administering Avastin and Sutent to lab mice with breast cancer. Both of these drugs halted the growth of blood vessels that typically feed a tumor. However, they also found these medications trigger the development of more cancer stem cells. Cancer stem cells help a tumor grow and spread and are highly resistant to drug therapy.

After the mice were treated with either drug, the researchers found that the number of cancer stem cells increased. They believe the cause of this phenomenon is due to a cellular response to low oxygen. The researchers were also able to determine the pathway that responded to low oxygen and activated these stem cells.

Avastin, which is FDA approved for several cancers, has had its approval for breast cancer therapy revoked. The Agency claims that the clinical trials had demonstrated that Avastin’s effects were not long-term; patients would soon relapse, with their cancer spreading at full force.

The authors believe that perhaps these drugs could be administered with a cancer stem cell inhibitor to boost their efficacy. They added that according to initial data from an ongoing study, this suggested approach appears to be effective.


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