NEW YORK (Reuters Health) -
The number of moles a woman has may be tied to her risk
of developing breast cancer, according to two new
studies.
The studies don’t prove that moles cause breast cancer or that women
with a lot of moles will definitely get breast cancer. Instead, they
suggest there may be a small genetic or hormonal link between the
two.
“This shouldn’t be a concern for women with moles, because we don’t
think the relationship is causal,” said Marina Kvaskoff, the lead
author of one of the new studies.
Kvaskoff is affiliated with INSERM - the French National Institute
of Health and Medical Research - and the University of Paris 11.
Researchers suspected that moles, also known as nevi, and breast
cancer might share links to certain hormones and genes. That would
mean moles could be used to help predict a woman’s breast cancer
risk.
“We always need to discover more causes of cancer and breast cancer
in particular,” Kvaskoff said. “If more studies were to find nevi
were associated with breast cancer risk, then nevi could become a
risk marker for breast cancer risk.”
In one of the studies, researchers led by Mingfeng Zhang at Brigham
and Women’s Hospital in Boston used data collected on 74,523 female
nurses between 1986 and 2010 to measure women’s breast cancer risk
by the number of moles on their arms.
Women with no moles had about an 8.5 percent chance of developing
breast cancer during the study, compared to an 11.4 percent chance
of breast cancer among women with 15 or more moles on their left
arm.
Among women who had already gone through menopause, Zhang and her
colleagues found those with six or more moles had higher levels of
estrogen and testosterone in their blood, compared to women without
moles.
After adjusting their data to account for the differing hormone
levels, the researchers found the link between moles and breast
cancer disappeared.
In the other study that was led by Kvaskoff, researchers found that
French women who reported having “very many moles” were 13 percent
more likely to develop breast cancer between 1990 and 2008 than
women who had no moles. That study included 89,902 total women.
The association disappeared after the researchers adjusted the data
to account for other breast cancer risk factors, including family
history of breast cancer.
Kvaskoff said the findings suggest that the link between the number
of moles a woman has and her risk of breast cancer could be genetic
or hormonal. Her team did not have the data to take hormones into
account, however.
The new studies, published in PLOS Medicine, are also limited
because they mostly relied on white women. Additionally, one study
asked women to report their own moles, which may be unreliable.
Kvaskoff said the magnitude of the associations the researchers
found was small, which suggests moles may not be an important risk
factor.
In an editorial accompanying the new studies, Barbara Fuhrman and
Victor Cardenas from the University of Arkansas in Little Rock write
that more research is needed.
They say that they hope additional studies will add information on
the relationship between moles and breast cancer, and help with the
assessment of breast cancer risk.
For now, Kvaskoff said the biggest risk of moles is skin cancer.
“Women in general should always get their moles checked for this
reason,” she said. “But it shouldn’t be a concern with breast
cancer.”
SOURCE: http://bit.ly/1pkIjK0,
http://bit.ly/1oOFCPc and http://bit.ly/1n6qd9I PLOS Medicine,
online June 10, 2014.
