FRIDAY, July 6 (HealthDay News) — Whether or not a woman becomes
pregnant while on fertility drugs may affect her odds for breast cancer
later on, a new study suggests.
However, experts who reviewed the study said it has flaws and is far
In the study, published July 6 in the Journal of the National Cancer
Institute, women using ovulation-stimulating fertility drugs who were
unable to get pregnant for at least 10 weeks had a lower risk of the
disease than women who have not taken the drugs, the U.S. study found.
On the other hand, the odds of breast cancer rose for women who became
pregnant for at least 10 weeks after taking the fertility drugs, when
compared to women who were unsuccessfully treated with these drugs.
However, the risk for women who became pregnant while on fertility
drugs rose only high enough to put it on par with women who had never
taken fertility drugs, the researchers noted.
The researchers, led by Chunyuan Fei, at the U.S. National Institute of
Environmental Health Sciences, examined women diagnosed with breast cancer
before the age of 50, as well as their sisters who did not have the
disease, over the course of two years.
“Our data suggest that exposure to a stimulated pregnancy is enough to
undo the reduction in [breast cancer] risk associated with a history of
exposure to ovulation-stimulating drugs,” the authors wrote.
The study’s authors pointed out that the study was limited by its
reliance on the participants’ self-reported fertility drug usage, and a
lack of information on each woman’s specific diagnosis for infertility.
The study is also complicated by the fact that it focuses on women who
developed breast cancer before the age of 50, and these tumors are often
associated with genetic factors.
In an accompanying editorial, Louise Brinton, of the division of cancer
epidemiology and genetics at the U.S. National Cancer Institute, noted
that the effects of one fertility drug are similar to an established drug
long used to prevent cancer — a finding that could help explain the study
Still, Brinton believes more research is needed to understand the link
between breast cancer risk and fertility drugs.
Two other experts took issue with the study’s methodology.
“It is hard to draw a conclusion as to whether or not treatment for
infertility increases the risk of breast cancer from this study,” said Dr.
Stephanie Bernik, chief of surgical oncology at Lenox Hill Hospital in New
York City. She said these types of cases-vs.-control group studies are
somewhat unreliable, and she pointed out that while some prior studies
looking at fertility drugs and breast cancer have found a link, others
“One of the ways to reach a better conclusion would be the creation of
a national data bank where information on women undergoing treatment is
entered and updated as time progresses,” Bernik said. “This is an
important question to answer, and better methods of obtaining the
information need to be established.”
For his part, Dr. Paul Tartter, a breast surgeon at St. Luke’s
Roosevelt Hospital Center in New York City, noted that “previous studies
have not found an increased risk [of breast cancer for women on fertility
treatment]. Only one previous study noted a slightly increased risk, which
was not statistically significant.”
He also took issue with the choice of control group included in the
“The control group for these women should be women of the same age who
became pregnant without IVF — they did not use the correct control group.
Using the patients’ sisters is irrelevant,” Tartter explained.
Furthermore, “the cases had significantly younger age at menarche [onset
of menstruation] and older age at first birth, both well-known risk
factors for breast cancer. Nowhere in this study did they control for
The American College of Obstetricians and Gynecologists provides more
information on infertility treatments.
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