Estrogen Brings Breast Cancer Back
Expert: Losing Estrogen-Making Fat Ups Breast Cancer Survival
March 7, 2008 -- Breast cancer survivors whose bodies make the least
estrogen have the lowest chance of breast cancer recurrence, a long-term study
Estrogen levels -- measured soon after initial breast cancer treatment --
were twice as high in women whose breast cancer returned as in those whose
breast cancer did not come back.
Nearly all the women in the study had already gone through menopause, and
most took the estrogen-blocking drug tamoxifen. So where did their estrogen
come from? Fat tissue, says study investigator Cheryl Rock, PhD, RD, a
professor in the cancer prevention program at the University of California, San
"Fat tissue is the primary non-ovarian site for estrogen production in
the body," Rock tells WebMD. "And what makes this worse is that the
elevated insulin levels associated with obesity are suppressing sex-hormone
binding globulin [which removes free estrogen from the circulation]."
All this is good news for breast cancer survivors, Rock says. It means that
by exercising and losing weight, they can cut their risk of cancer
"Anti-estrogen drugs are not going to solve this problem for everybody,
so let's look for the lifestyle issues that can help," she says.
"Exercise and losing weight gives breast cancer survivors two bangs for the
buck. You not only reduce estrogen from fat -- the main organ making estrogen
in postmenopausal women -- but you improve your heart health, too."
Rock's advice makes a lot of sense to Charles Cox, MD, a surgical oncologist
in the breast program at Tampa's Moffitt Cancer Center.
"Exercise and reducing weight can be an effective therapy for breast
cancer patients because this lowers their overall stores of estrogen," Cox
tells WebMD. "This puts patients in charge of their own life expectancy.
What they do doesn't just reduce their odds of cancer recurrence: It improves
their overall outcome."
The study by Rock and colleagues looked at baseline estrogen levels in 153
breast cancer survivors whose breast cancer returned and in 153 age- and
cancer-stage-matched women whose breast cancer did not come back. All of the
women were followed for more than seven years as part of a study of how diet
affects breast cancer recurrence.
Rock and colleagues report the findings in the March issue of the journal
Cancer Epidemiology, Biomarkers, and Prevention.