Women getting fertility treatments can be reassured that in-vitro fertilisation (IVF) does not increase their risk of breast and
gynaecological cancers, according to a new study of Israeli women.
"The findings were fairly reassuring. Nothing was
significantly elevated," said lead author Louise Brinton, chief of the
Hormonal and Reproductive Epidemiology Branch at the National Cancer Institute
in Rockville, Maryland. Still, she added, "We should continue to monitor
these women."IVF treatments can involve ovulation-stimulating drugs or
ovary puncturing to collect eggs - procedures that researchers have suspected
may increase women's risk of cancer.
Indeed, previous studies linked IVF early in life to
heightened risks of breast cancer and borderline ovarian tumors. But other
studies found little connection between fertility treatments and cancer.
The association has been difficult to untangle, experts
said, in part because it's hard to know whether unmeasured factors not related
to IVF itself may affect the risk of cancer in women who have trouble
conceiving. And so far, there haven't been a lot of women who developed cancer
after fertility treatment included in studies.
"We all want answers, but it's a very difficult
exposure to study, particularly when we don't have the numbers we would really
like," Brinton said.
To boost those study figures, she and her colleagues examined
the medical records of 67 608 women who underwent IVF treatments between 1994
and 2011 and 19 795 women who sought treatment but never received IVF.
What the research
The researchers linked those women's files to a national
cancer registry and found 1,509 of them had been diagnosed with cancer through
mid-2011.There was no difference in women's chances of being diagnosed with
breast or endometrial cancer based on whether they were treated with IVF.
The researchers did find a woman's risk of ovarian cancer
slightly increased the more rounds of treatment she received, they wrote in the
journal Fertility and Sterility. But that finding could have been due to
Brinton said her study was too small to conclusively link
IVF and ovarian cancer - and that it remained very rare, with 45 cases in the
A similar association was found in a study headed by Dr
Bengt Kallen, director of the Tornblad Institute at Lund University, Sweden.
Kallen, who was not involved in the current research, said
any increased ovarian cancer risk might be due to the dysfunctional ovaries
"Infertile women have a primary problem with their
ovaries and IVF has nothing to do with it," Kallen said. "It's a
rather difficult thing to disentangle if there is an effect from the hormones
or from the IVF procedure."
Dr Sherman Silber of the Infertility Center of St. Louis
warned these types of studies have several biases that could make the results
difficult to interpret.
For example, women undergoing IVF are watched extra closely,
which would likely increase the chance that ovarian cancers are detected, said
Silber, who also was not involved in the new study.
"You have to be extraordinarily cautious about this
kind of a study," Silber said. "If anything, it's reassuring. One
doesn't see any real increase in cancer."
Researchers said future studies would require larger groups
of IVF-treated women to tease out potential long-term risks.
"What is surprising all of us who are working in this
area is how almost every study gets a different answer," Brinton said.
"There's a need for monitoring, but we also shouldn't
get too alarmed at this early stage."