The large study did not find an overall increased risk of these cancers, but did pinpoint a slight increase in risk of non-invasive breast cancer, and ovarian tumours in women who had fertility treatment. The increase in risk for non-invasive breast cancer, which does not grow into normal tissues or spread throughout the body, was associated with the number of treatment cycles a woman had. The increase in the risk of ovarian tumours appeared to be confined to women with other known risk factors for developing this type of cancer.
In the study, Professor Alastair Sutcliffe at University College London and his team used records of the Human Fertilisation and Embryology Authority of more than 250,000 British women who underwent an assisted fertility treatment between 1991 and 2010, linking this data to information obtained from national cancer records.
The team observed the women over an average of 8.8 years. The average age at the time of treatment was 34.5 years, with women having an average of 1.8 treatment cycles. The cause of infertility among the participants studied involved at least one female factor 44 percent of the time and male factors in 33 percent of cases. In 19 percent of cases the cause of infertility was unexplained.
Assisted reproduction techniques using high levels of hormones have long been thought to potentially increase the risk of cancer in women. A landmark study in 2015 seemed to confirm this by finding that the ovarian cancer risk of women undergoing fertility treatment increases by a third.
The authors of the current paper suggest that underlying patient characteristics, rather than the treatment itself, is likely to explain the previous findings. However, the authors acknowledge the limitations of observational studies, highlighting that continuous monitoring of the population who have fertility treatment is essential.
The research was published in the BMJ.