SAN DIEGO, March 7 (UPI) -- Estrogen levels were almost twice as high in the blood of breast cancer patients with recurring cancer, as in those who were cancer free, a U.S. study said.
Researchers studied data from 3,088 participants in the Women's Healthy Eating and Living Study -- comparing 153 women whose cancer had recurred with 153 breast cancer patients who were cancer-free on the basis of several variables such as age and use of chemotherapy.
Women whose breast cancer came back after treatment had almost twice as much estrogen in their blood than did women who remained cancer-free.
"Women who have already been treated for breast cancer should do as much as they can do to reduce estrogen in their blood, such as exercising frequently and keeping weight down," lead author Cheryl L. Rock of the University of California, San Diego, said in a statement. "Taking anti-estrogen drugs like tamoxifen may not completely wipe out the hormone's effect in women who have high levels of estrogen."
High levels of estrogen are known to increase risk of initial development of breast cancer.
The finding are published in Cancer Epidemiology, Biomarkers and Prevention.
