Drug Re-Sensitizes Breast Tumors to Treatment

Phase II study finds sorafenib helps reverse disease resistance to anti-hormonal therapy

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FRIDAY, Sept. 5 (HealthDay News) -- The drug sorafenib may help "re-sensitize" certain breast cancer tumors to anti-hormonal drugs, Georgetown University Medical Center researchers say.

Women with estrogen-receptor or progesterone-receptor positive (ER or PR positive) metastatic breast cancers often take anti-hormonal medicines, such as aromatase inhibitors, to keep the cancer under control. Aromatase inhibitors lower the amount of estrogen in the body.

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However, the tumor eventually becomes resistant to anti-hormonal drugs, and the cancer begins to grow.

"At first, the tumor's growth is halted, because the aromatase inhibitor is depriving the cancer of the estrogen it needs to grow. Eventually, though, the cancer will figure out another way to thrive in the absence of the estrogen," Dr. Claudine Isaacs, clinical director of the breast cancer program at Georgetown University Medical Center's Lombardi Comprehensive Cancer Center, said in a university news release.

Isaacs and her colleagues wanted to find out if a new approach can restore the effectiveness of anti-hormonal drugs against these tumors.

The phase II study included 27 postmenopausal women with metastatic breast cancer that had recurred or progressed while the women were taking the aromatase inhibitor anastrozole. Preliminary analysis of study data showed that 26 percent of the women showed a clinical benefit response while taking both sorafenib and anastrozole.

"Given what we know about the ineffectiveness of sorafenib alone in metastatic breast cancer, we believe the benefit that we're seeing may be attributable to the restoration of sensitivity to aromatase inhibitors," Isaacs said. "To manage breast cancer long-term, it's apparent that we may need to continually switch drugs to keep up with how a cancer evolves and evades each approach. In a sense, for each step back, we hope to take two steps forward."

The study was to be presented Sept. 5 at the 2008 ASCO Breast Cancer Symposium in Washington, D.C. Isaacs is part of the speaker's bureau for Pfizer Inc., which makes the aromatase inhibitor Exemestane.

More information

The U.S. National Cancer Institute has more about breast cancer treatment.

-- Robert Preidt