Breast Cancer Growth Regulator Holds Promise For More Targeted Treatment

Published in a recent issue of the American Association of Cancer Researcher's journal Cancer Research, the study focused on how decreased concentrations of sEGFR can indicate the effectiveness of letrozole.

In women with postmenopausal breast cancer, the hormone estrogen often stimulates tumor growth. Letrozole, which is currently used in breast cancer therapy, stops the local production of estrogen, therefore reducing tumor growth. To monitor the effectiveness of this drug's reduction in tumor growth, estrogen levels are measured. In postmenopausal women with breast cancer, estrogen can be difficult to measure because the levels are already quite low. The Yale team, led by Nita J. Maihle, professor in the Department of Obstetrics, Gynecology & Reproductive Sciences, discovered sEGFR, another regulator of breast cancer growth that can be used to measure responsiveness to treatment.

Maihle and her colleagues collected blood samples from postmenopausal women with metastatic breast cancer before treatment with letrozole and then one month and three months after letrozole therapy. The team measured sEGFR concentrations in these blood samples and found that after one month of letrozole therapy, sEGFR decreased in 73 percent of patients and after three months of letrozole therapy, sEGFR concentrations decreased in 76 percent of patients when compared to pretreatment levels.

"Unfortunately, the number of patients (43) involved in this study was not large enough to evaluate how these changes in sEGFR levels predict a patient's cancer progression or survival," said Maihle. "Since the FDA recently approved letrozole for the treatment of breast cancer, larger studies are needed to determine its clinical utility."

"Ultimately, we hope to provide the most effective ways to determine who will respond to this new breast cancer therapy," added Maihle, who is also affiliated with Yale Cancer Center.

Other authors on the study included Jacqueline M. Lafky, Andre T. Baron, Elsa M. Cora, David W. Hillman, Vera J. Suman, Edith A. Perez and James N. Ingle.

Citation: Cancer Research 65, 3059-3062, (April 15, 2005).