There are no overall increases in the risk of womb cancer or invasive breast cancer after assisted reproduction, according to a study of over 250,000 British women.
Small increased risks of non-invasive breast and ovarian tumours were found, but the researchers said these results may not be due to the treatment itself and require further investigation.
“No increased risk of corpus uteri or invasive breast cancer was detected”
They noted that assisted reproduction usually involved exposure to high levels of hormones, which can carry an increased risk of breast, endometrial, and ovarian cancers.
But they highlighted that the results of previous studies on risks of reproductive cancers in women who had undergone assisted reproduction were inconsistent.
The team, led by Professor Alastair Sutcliffe at UCL Great Ormond Street Institute of Child Health, investigated the risks of ovarian, breast and womb – corpus uteri – cancer in women who have had assisted reproduction.
Using Human Fertilisation and Embryology Authority records, they identified all women who had assisted reproduction in Britain between 1991 and 2010 and then linked them to national cancer records.
In total, 255,786 women were followed up over an average of 8.8 years. 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 study, published in the British Medical Journal, found no overall increased risk of breast cancer or invasive breast cancer associated with assisted reproduction, compared with the general population.
“Ongoing monitoring of this population is essential”
An increased risk of non-invasive (in situ) breast cancer was detected – an absolute excess risk of 1.7 cases per 100,000 person years – which was associated with an increasing number of treatment cycles.
An increased risk of ovarian cancer, both invasive and borderline, was also detected – an absolute excess risk of five cases per 100,000 person years.
However, this was limited to women with other known risk factors, which the researchers suggested may be due to underlying patient characteristics, rather than assisted reproduction itself.
The study authors highlighted that, while they found no overall increased risk of womb cancer, ongoing monitoring of “these important outcomes in this ever growing population is essential”.
The study authors stated: ”In this large, national population based study of British women after assisted reproductive technology treatment, no increased risk of corpus uteri or invasive breast cancer was detected.