Women in the United Kingdom who had assisted reproduction are at greater risk of developing ovarian cancer and in situ breast cancer than the general population, a study found.
But researchers attribute this to patient characteristics or increased surveillance among these women, rather than the procedure itself.
Their study, “Risks of ovarian, breast, and corpus uteri cancer in women treated with assisted reproductive technology in Great Britain, 1991-2010: data linkage study including 2.2 million person years of observation,” was published in the medical journal BMJ.
Sex hormones have a well-recognized role in cancers of the breast and reproductive system. Therefore, the increased use of assisted reproductive techniques — which use hormones to stimulate the ovaries and involve multiple ovarian punctures — have raised concerns regarding cancer risk.
Studies have yielded inconsistent results, and the association between assisted reproduction and the risk of cancers remains unclear.
A team from University College London sought to study the risks of ovarian, breast, and endometrial cancer in women who had assisted reproduction.
They studied 255,786 women who had assisted reproduction in Great Britain between 1991 and 2010. The records, provided by the Human Fertilisation and Embryology Authority (HFEA), included a median follow-up time of nearly nine years.
Researchers compared cancer rates with national incidence rates for the general female population of England and Wales.
The women in the study had received their first treatment at a mean age of 34.5. Most (44%) were receiving assisted reproduction due to female factors, while 33% were having it due to male factors. In 19% of cases, the reason for infertility was unknown.
Overall, breast cancer did not increase in the assisted reproduction population. However, a longer post-treatment period was linked with a lower risk of breast cancer.
Looking at breast cancer by type, researchers found that a localized form called in situ breast cancer increased by 15% in women who had assisted reproduction, and that this association was dependent on the number of treatment cycles a woman had received.
The incidence of endometrial cancers was also similar in these women and the general population.
But women whose infertility was caused by an ovulatory disorder were 59% more likely to develop endometrial cancers.
The overall risk for ovarian cancer was 39% higher in the study population, researchers found. The risk was higher across most age groups at first treatment, but women who received the treatment at a younger age had the greater risk.
The risk was also higher for women whose infertility was caused by a female factor — such as endometriosis or tubal disease — but not for women with a male factor or unknown infertility.
When tumors were classified as invasive or borderline (tumors with both malignant and non-malignant characteristics), both were higher in women who had received assisted reproduction.
Still, these increases were limited to women with other risk factors, such as endometriosis and still birth, suggesting “that this finding is more likely due to underlying patient characteristics, rather than assisted reproduction itself,” investigators said.
Nonetheless, researchers did not rule out that excess surveillance or the reproductive treatment might have caused the excess ovarian cancer cases seen in the study.
Additional research is necessary and “ongoing monitoring of this population is essential,” investigators wrote.