High levels of
Estrogen associated with Breast Cancer
recurrence
Newswise — Women whose
breast cancer came back after treatment had
almost twice as much estrogen in their blood
than did women who remained cancer-free –
despite treatment with anti-estrogen drugs
in a majority of the women –according to
researchers in a study published in the
March issue of Cancer Epidemiology,
Biomarkers and Prevention, a journal of
the American Association for Cancer
Research.
The findings suggest
that high levels of estrogen contribute to
an increased risk of cancer recurrence, just
as they lead to the initial development of
breast cancer, said the study’s lead author,
Cheryl L. Rock, Ph.D., a professor in the
Department of Family and Preventive Medicine
at the University of California, San Diego.
“While this makes
sense, there have been only a few small
studies that have looked at the link between
sex hormones in the blood and cancer
recurrence,” she said.
“This is the
largest study to date and the only one to
have included women taking agents such as
tamoxifen to reduce estrogen’s effect on
cancer growth.
“What the results mean
for women who have already been treated for
breast cancer is that they should do as much
as they can to reduce estrogen in their
blood, such as exercising frequently and
keeping weight down,” she added.
“Taking anti-estrogen
drugs like tamoxifen may not completely wipe
out the hormone’s effect in women who have
high levels of estrogen.”
Participants from this
study were drawn from the larger Women’s
Healthy Eating and Living Study (WHEL), a
dietary intervention trial that followed
3,088 women who had been treated for early
stage breast cancer but who were cancer-free
at the time they enrolled. Participants were
randomly assigned to one of two groups – one
that ate a “normal” healthy diet and the
other that ate extremely high amounts of
fruits, fiber, and vegetables – and were
followed for more than seven years.
Breast cancer
recurrence was about the same in each group,
according to the results, published in 2007.
Researchers interpreted the findings to mean
that a normal diet that incorporates the
U.S. Food and Drug Administration guidelines
for recommended amounts of fruits and
vegetables is sufficient.
In the current nested
case-control study, 153 WHEL participants
whose cancer had recurred were matched with
153 participants who remained cancer-free.
These pairs were alike in terms of tumor
type, body size, age, ethnicity, use of
chemotherapy and other variables. Two-thirds
of the participants were using tamoxifen,
Rock said.
When they enrolled,
researchers tested the women’s blood for
concentrations of the steroid hormones
estradiol (the primary human estrogen) and
testosterone.
They analyzed
different forms of estradiol and
testosterone in the blood, such as how much
was bound to transport proteins (such as to
the sex hormone binding globulin, or SHBG)
and how much was “free” circulating and able
to enter a cell.
Researchers found that
higher estradiol concentrations, in all
forms, significantly predicted cancer
recurrence. Overall, women whose cancer came
back had an average total estradiol
concentration that was more than double the
average for women who remained cancer-free.
Increased levels of
testosterone or SHBG levels were not
associated with recurrence, contradicting
the findings of several previous studies.
Although genetic and
metabolic factors likely influence the
relationship between circulating sex
hormones and risk of breast cancer
recurrence, Rock said the study provides
solid evidence that higher concentrations of
estradiol in the blood contribute to risk
for breast cancer recurrence.
The Walton Family
Foundation, the National Cancer Institute,
and the National Institutes of Health funded
the study.
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