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Fertility treatment does not appear to raise serious cancer risk

Small higher risk of non-invasive breast and ovarian tumours may not be due to treatment

Adrian O'Dowd

Thursday, 12 July 2018

Women who undergo fertility treatment do not appear to have a higher risk of developing womb cancer or invasive breast cancer, suggests a study* involving more than 250,000 women published today by The BMJ.

Assisted reproduction is common worldwide and more than five million children have been born as a result, but it usually involves exposure to high levels of hormones, which can carry an increased risk of breast, endometrial (womb), and ovarian cancers.

Previous studies on risks of reproductive cancers in women who have undergone assisted reproduction have shown inconsistent results.

Therefore, a team led by Professor Alastair Sutcliffe at UCL Great Ormond Street, Institute of Child Health in London, set out to investigate the risks of ovarian, breast and womb (corpus uteri) cancer in women who have had assisted reproduction.

Using Human Fertilisation and Embryology Authority (HFEA) records, they identified all women who had assisted reproduction in Britain between 1991 and 2010 and then linked this information to national cancer records.

For the study, 255,786 women were followed up over an average of 8.8 years. The average age at first treatment was 34.5 years and women had an average of 1.8 treatment cycles.

Cause of infertility involved at least one female factor in 111,658 (44%) women. Infertility was unexplained in 47,757 (19%) women, and was due only to male factors in 84,871 (33%).

The team found no overall increased risk of breast cancer or invasive breast cancer associated with assisted reproduction, compared with the general population.

However, a small increased risk of ovarian cancer – both invasive and borderline – was detected (absolute excess risk of five cases per 100,000 person years), but this was limited to women with other known risk factors, suggesting this may be due to underlying patient characteristics, rather than assisted reproduction itself.

An increased risk of non-invasive (in situ) breast cancer was detected (absolute excess risk of 1.7 cases per 100,000 person years), which was associated with an increasing number of treatment cycles.

The researchers found no overall increased risk of womb cancer.

Because this was an observational study, no firm conclusions can be drawn about cause and effect, but the authors said strengths of their study included the large sample size and long follow up period, which enabled them to take into account potentially influential factors.

They concluded: “Increased risks of ovarian cancer, both invasive and borderline, were observed but limited to women with other known risk factors; these findings require further investigation.”

*Williams C, Botting B J, Sutcliffe A, et al. 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. BMJ 2018; 362 :k2644. DOI:10.1136/bmj.k2644

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