Reduced Levels of Fat in the Diet May Decrease
the Risk of Breast Cancer Recurrence According to New Clinical
Trial
Postmenopausal women who reduce their consumption of dietary fat
and have been treated for early-stage breast cancer may reduce
their chances for breast cancer recurrence or a second breast cancer,
according to results from the Women’s Intervention Nutrition
Study (WINS). WINS was the first large-scale randomized trial
to show that a change in diet can improve breast cancer outcomes
in women who are receiving conventional treatment for early-stage
breast cancer. Results of this study, which was sponsored
by the National Cancer Institute (NCI), part of the National Institutes
of Health, appear in the December 20, 2006, issue of the Journal
of the National Cancer Institute* along
with an editorial on the findings by NCI scientists**. This
report is based on an interim analysis of the trial data.
The WINS study investigated a subset of women who have already
been diagnosed with breast cancer and who were willing to enroll
in a study to see if lowering fat in their diet would reduce the
risk of their cancer recurring. Earlier in 2006, the Women’s
Health Initiative (WHI), which examined the effect of a low fat
diet on breast cancer risk, showed a trend toward a modest benefit
of a reduced-fat diet on the incidence of invasive breast cancer.
“The relationship between dietary fat and breast cancer
has been unclear,” said NCI Director John E. Niederhuber,
M.D. “Certainly there is accumulating evidence that a healthy
lifestyle — reduced fat consumption and exercise — is
a worthy goal, to decrease risk and to optimize long-term therapy
outcome.”
WINS enrolled 2,437 women between 1994 and 2001 who had been treated
for early-stage breast cancer. The women, ages 48 to 79, were randomly
assigned to a lower-fat dietary intervention group or a control
group who ate their regular diet.
At the start of the study, both groups consumed similar amounts
of calories from fat; about 57 grams of fat per day or close to
30 percent of daily caloric intake. At the end of the first year
of observation, the women in the dietary intervention group had
reduced their fat intake by an average of 24 grams per day compared
with only a 5 gram per day drop in the control group. The difference
between the two groups was maintained throughout the trial. By
the fifth year of the trial the women in the intervention group
weighed an average of 6 pounds less than the women in the control
group. Three more years of follow-up are currently being planned.
After a median of five years of follow-up, breast cancer recurrence
or new breast cancers occurred in 9.8 percent of the women on the
low-fat diet and in 12.4 percent of those on the standard diet.
This amounted to a 24 percent reduction in the relative risk of
recurrence for the women on the low-fat diet. The largest
risk reduction — 42 percent — appeared to be among
women on the low-fat diet whose tumors did not respond to the presence
of the hormone estrogen. The risk reduction was 15 percent in women
who did respond to estrogen. Breast cancer that doesn’t respond
to estrogen is called estrogen receptor negative (ER-negative)
and usually has a poorer outcome than ER-positive disease. “Reductions
were predicted in women with ER-positive disease because of the
association between fat intake and estrogen levels but the effect
on ER-negative disease is, if verified, a surprising and potentially
important observation regarding breast cancer and signals a possible
new avenue of research,” said John Milner, Ph.D., Chief of
the Nutritional Science Research Group at NCI.
“These results suggest that an intervention aimed at reducing
dietary fat consumption can reduce the risk of breast cancer recurrence,” said
principal investigator Rowan T. Chlebowski, M.D., Ph.D., of the
Los Angeles Biomedical Research Institute in California. “Although
further confirmation is needed, a low-fat diet may offer other
health benefits, such as modest weight loss.”
“In both WHI and WINS studies, it took about four years
to detect a reduction in risk so clearly these are not immediate
effects,” said Milner. “It is also clear that some
women benefit a lot more than others from a reduction in dietary
intake of fat, possibly because a person’s genetics may well
be setting the tone for the benefits of dietary intervention.” He
also emphasized that a reduction in fat is just one of many dietary
modifications that may influence the development of cancer.
In the accompanying editorial, Anne C.M. Thiébaut, Ph.D.,
et al. at NCI, discuss various study limitations, including the
use of self-report to track diet and possible imbalances in treatment
between the two study groups. They also note the difficulty
of conducting clinical trials where very dramatic lifestyle changes
are involved, but conclude that WINS produced very important results
for future consideration.
Funding for this study was primarily provided by the NCI’s
Division of Cancer Prevention. Funding for supplemental projects
was provided by the Breast Cancer Research Foundation and the American
Institute for Cancer Research.
For more information about cancer, please visit the NCI Web site
at http://www.cancer.gov,
or call NCI's Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov. |