Kate Johnson

October 26, 2015

BALTIMORE — In women who undergo in vitro fertilization (IVF), the risk for cancer is minimal, according to a large study.

"Overall, this study suggests that there is little for women to worry about regarding the risk of cancers and the drug treatments they undergo to have a baby with IVF," said Alastair Sutcliffe, MD, from the Institute of Child Health, University College London, United Kingdom.

Despite this reassuring statement, he delivered what he called "a measured conclusion," given that, at first glance, the results suggest that the risk for ovarian cancer is increased.

However, "most analyses of this huge dataset suggest that this increased risk was principally because of the nature of women needing these treatments in the first place (their underlying risk factors) and not due to the hormone drug treatments themselves," Dr Sutcliffe told Medscape Medical News.

He presented the study findings as a prize paper here at the American Society for Reproductive Medicine 2015 Annual Meeting.

Dr Sutcliffe and his colleagues used the Human Fertilization and Embryology Authority registry to identify all women in the United Kingdom who used assisted reproductive technology from 1992 to 2010. They linked those data to the National Health Service Central Registers, which records all cancers and deaths in England, Scotland, and Wales.

The team evaluated 255,786 records, which represented 2.2 million women-years of exposure.

Reproductive technology was associated with an elevated risk for ovarian cancer when the 386 observed cases were compared with the 282 expected cases (standardized incidence ratio [SIR], 1.37).

"Mixed" News

But after a deeper analysis, the researchers determined that the findings are "mixed," Dr Sutcliffe reported.

The risk for ovarian cancer did not increase as the number of cycles increased (hazard ratio [HR], 1.02), which supports the safety of assisted reproductive technology, he explained. "If this was caused by hormonal therapies from assisted reproductive technologies, you would expect an increase."

Although the risk for ovarian cancer did increase with decreasing parity (HR, 0.80), with the greatest risk in nulliparous women (SIR, 1.54), "this is known about ovarian cancer as a whole," he added.

There was an elevation in the risk for ovarian cancer when female infertility was an issue (SIR, 1.62), but not male infertility (SIR, 1.05). This, too, points away from a causal effect of assisted reproductive technology, Dr Sutcliffe said.

The was no significant association between assisted reproductive technology and breast cancer (SIR, 0.98) or endometrial cancer (1.12).

"Endometriosis was a significant risk (SIR, 2.35; HR, 1.82), but that, again, is something that's been suggested in the literature," he explained.

But there was one "slightly worrying" observation in the dataset that suggests potential risk related to the treatments, Dr Sutcliffe said.

The risk for ovarian cancer was significantly greater in women who underwent their first treatment at a younger age (P trend < .0001), and was greatest in the 3 years after the first treatment (SIR, 1.54).

"This is a large, population-based study conducted by a team of distinguished researchers," said Barbara Luke, ScD, an epidemiologist from Michigan State University in East Lansing.

"Their findings confirm many of the known risk factors for ovarian cancer, such as lower parity and endometriosis, which adds strength to the association," she told Medscape Medical News.

"The increased risk of ovarian cancer that Dr Sutcliffe's team found may be greater, in part, because they chose to include borderline tumors, which in other studies are often excluded," she added.

In fact, Dr Luke reported, a recent population-based study that did not include borderline tumors showed no increased risk for cancer (Hum Reprod. 2015;30:1952-1963).

Dr Sutcliffe and Dr Luke have disclosed no relevant financial relationships.

American Society for Reproductive Medicine (ASRM) 2015 Annual Meeting: Abstract O-93. Presented October 20, 2015.

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