Breast cancer is undoubtedly a source of anxiety and fear for many women, as it remains one of the most common cancers in the world, affecting about 1 in 8 women. As the breast gland is sensitive to both oestrogen and progesterone, the two main female hormones, many studies have examined the possibility of a link of hormonal treatments and breast cancer.

As the number of women receiving hormonal drugs to treat infertility continues to rise worldwide, it is important to note that ovarian stimulation drugs may increase both oestrogen and progesterone production. In most cases this may not have any consequences, but occasionally, some breast cells may become activated and even get to form breast tumours in the future.

So far, no clear link has been shown to exist between ovarian stimulation drugs and breast cancer.

A good number of studies have looked into the association between hormonal drugs for infertility and breast cancer without any increased risk being clearly established. Of note, what appears to be a significant factor in favour of developing a malignant breast tumour is infertility itself, regardless of any hormonal medicines having been used.

The two most commonly studied infertility drugs so far have been clomifene citrate and gonadotropins. Clomifene citrate, in the form of a tablet, has been in use for a good number of years, as a mild form of ovarian stimulation, especially useful in cases of ovulation problems, such as in polycystic ovarian syndrome. The gonadotropins are hormonal drugs that you use as injections, during ovarian stimulation, especially during IVF treatment. A recent study published in July, in the Fertility and Sterility Journal (https://doi.org/10.1016/j.fertnstert.2021.01.044), comparing the risk of breast cancer between women having taken clomifene or gonadotropins with women who have never used such medicines has found no link between the use of these hormonal treatments and risk of breast cancer.

However, it is important to note that previous studies have highlighted a different risk of breast cancer in specific groups of women who are having hormonal infertility treatment. In particular, age at start of fertility treatment was suggested as an important factor, as well as having hormonal infertility treatment and a twin pregnancy as a result. Although these findings were not reproduced and confirmed afterwards, it is reasonable to keep hormonal stimulation doses to the lowest needed in young ages, while every effort should be made to keep the possibility of multiple pregnancies as low as possible, as well.

A common question that doctors get to answer during infertility consultations is about the number of IVF cycles and the dose of hormonal medications that is thought to be safe, especially regarding the risk of breast cancer in future. So far, no such information is available from the studies performed. However, it is important to counsel women about the benefits from any specific hormonal treatment compared to any potential risks, breast cancer risk included. When the chances of having a pregnancy through conventional IVF is considerably small it is essential to explore alternative options and discuss these in detail. 

As far as hormonal doses are concerned, it is encouraging to note that many clinics now worldwide adopt mild ovarian stimulation treatments, as results in many cases are quite similar with more conventional hormonal doses used. 

In any case, what remains the most important issue is this of breast cancer screening tests. Women at higher risk to develop breast cancer, either due to their family history, or because of their diet and excess weight should have regular breast screening tests, especially if having difficulty getting pregnant and receiving, or having received hormonal treatments.

©2021, Nicholas Christoforidis, Fertility Matters
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