This study, published in the March issue of Cancer Epidemiology, Biomarkers & Prevention, followed 153 pairs of women who had had breast cancer (one in each pair experienced a recurrence, while one did not) for more than seven years.
Two-thirds of the participants were using tamoxifen, a drug which interferes with estrogen's activity in the body.
In the end, women with more circulating estrogen were more likely to have a recurrence.
There may be other factors at play also, Rock said. For instance, sex hormone-binding globulin basically makes estrogen available to get into tissue. "If estrogen is bound to that protein, it's not going to float right over to the cell," Rock said. "When people are overweight, they have higher blood levels of insulin, which suppresses synthesis of that protein, so exercise not only is related to actually helping weight management but, because it lowers insulin, it might make the hormonal situation look better."
And don't rule out existing anti-estrogen drugs, experts added.
"This study justifies the use of drugs that help decrease estrogen levels like tamoxifen and aromatase inhibitors," Wu said. "[In the future], we may want to titrate different levels of anti-estrogen medications. Right now, we have a standard dosage for everyone, whereas women who are heavier or other women who may have higher estrogen levels for one reason or another may need larger doses."
Visit the National Cancer Institute for more on breast cancer.
SOURCES: Cheryl L. Rock, Ph.D., professor, family and preventive medicine, University of California, San Diego, School of Medicine; Jennifer Wu, M.D., obstetrician/gynecologist, Lenox Hill Hospital, New York City; March 2008, Cancer Epidemiology, Biomarkers & Prevention <
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