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In the analysis of data from 17 past studies, researchers found that
women who had ever breastfed their children were 11 percent less
likely than women who had children but didn’t breastfeed to be
diagnosed with endometrial cancer.
Longer breastfeeding seemed to further lower endometrial cancer
risk, though there was little extra benefit past 6-9 months of
breastfeeding, the study team reports in Obstetrics and Gynecology.
“Cancer of the uterus is becoming more common and we need to try to
prevent it,” said lead author Susan Jordan of the QIMR Berghofer
Medical Research Institute in Brisbane, Australia.
Endometrial cancer is the fourth most common cancer in women in
high-income countries such as the United States, Canada and
Australia, according to the International Agency for Research on
Cancer.
“The more women know about the things they can do to reduce their
risks of future cancer diagnoses, the better,” Jordan said by email.
“Although this piece of evidence by itself may not convince women to
breastfeed, it contributes to the overall picture of health gains
that can come from breastfeeding.”
The World Health Organization recommends that women exclusively
breastfeed for the first six months of their baby’s life, then
continue breastfeeding even after beginning to introduce solid
foods.
The researchers analyzed pooled data from studies participating in
the Epidemiology of Endometrial Cancer Consortium, including 10 from
the United States and others from Canada, Europe, China and
Australia. They looked at more than 26,000 women who had ever had a
child, whether they breastfed, and for how long. This included about
9,000 women with endometrial cancer.
After accounting for other factors that can influence endometrial
cancer risk, including age, race, education, oral contraceptive use,
menopausal status, years since last pregnancy and body mass index
(BMI), researchers found the apparent protective effect of
breastfeeding remained.
Notably, the risk reduction linked to breastfeeding was 28 percent
among women born after 1950, but negligible among those born before
1950, which may reflect differences in breastfeeding practices, they
study authors note. In the United States in the 1950s and 1960s, for
example, breastfeeding rates were much lower than in recent decades,
the authors note.
The study doesn’t prove that breastfeeding helps to protect against
endometrial cancer, but it’s plausible, the authors write, because
the growth of this type of cancer is stimulated by estrogen, which
is suppressed during breastfeeding.
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“The message is not only relevant for women making decisions about
breastfeeding but also for society to understand the benefits so we
can support women to breastfeed for reasonably long periods of
time,” Jordan told Reuters Health. “However, it’s not always
possible for women to breastfeed, so it should also be noted that
just because a woman chooses not to or can’t breastfeed, it doesn’t
mean she’ll go on to develop cancer.”
“Breastfeeding seems to significantly reduce the risk, but further
studies originating in other countries are required to assess the
association,” said Lianlian Wang of The Fourth Affiliated Hospital
of China Medical University in Shenyang, China, who was not involved
with the study.
For instance, the most recent endometrial cancer report produced by
the World Cancer Research Fund and American Institute for Cancer
Research in 2013 classified the evidence for a benefit from
breastfeeding as “limited-no conclusion.”
Jordan and colleagues are working with international collaborators
to investigate the effects of breastfeeding on ovarian cancer risk.
They’re also researching other factors that may influence the risk
of endometrial cancer, including specific medications.
“Breastfeeding has consistently been found to be associated with
reduced risk of breast cancer,” Jordan pointed out. “This provides
evidence of another long-term health benefit for women who
breastfeed for more than six months.”
SOURCE: http://bit.ly/2rFNGeL Obstetrics and Gynecology, June 1,
2017.
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