Breast Cancer

Breast cancer is the most common cancer affecting women with a lifetime risk of around one in eight and for reasons that are not clear, the incidence is increasing. Advances in the treatment of breast cancer have resulted in improved outcomes with around an 18% reduction in mortality in the last decade. However, heart disease is by far the biggest cause of death in women accounting for 47% of all deaths compared to 3% due to breast cancer.

Am I at risk of Breast Cancer if I take HRT?

The perceived risk of breast cancer is often the main reason women are not prescribed HRT. However, the evidence around the menopause, HRT and breast cancer is contradictory and confusing.

The WHI studies have contributed much to the confusion in this area. The first WHI publication in 2002 reported on women receiving HRT with conjugated equine oestrogen (CEE) plus continuous medroxyprogesterone acetate (MPA or Provera) and reported a significant increase in the incidence of breast cancer. However, the second arm of the study published two years later showed that women receiving oestrogen alone without MPA, because they had had a hysterectomy, did not have an increase in breast cancer.

The WHI had many flaws. The women recruited were relatively older and on average were above the age of 60 years, or more than ten years had passed since their menopause. In reality, the vast majority of women start taking HRT when they first develop symptoms, which is 1-2 years before or shortly after the menopause. Many women in these studies were overweight which we know is another risk factor for breast cancer. More importantly, the hormones used in these studies, CEE and MPA are hormones that are not much used today. Furthermore, this study could not determine whether the reported risk in women receiving this form of combined HRT was due to the type of oestrogen type, type of progestogen, or due to the continuous combined regimen used in this study.

A more recent report from the same group published in 2020 with a 20-year follow-up again showed that combined oestrogen and Provera resulted in an increased incidence of breast cancer, but there was no significant increase in mortality from breast cancer. This may be because women receiving HRT are diagnosed earlier when treatment is more successful. Those women who received oestrogen alone had a significant reduction in the incidence of breast cancer with an associated reduction in the risk of mortality after 20 years of follow-up.

While studies show an increase in the risk of breast cancer in women taking combined oestrogen and progesterone therapy,  it is important to note that this is small and less than the risk associated with obesity or moderate alcohol consumption. It is also important to bear in mind the significant benefits of HRT which include the alleviation of symptoms, improved quality of life, as well as the  reduction in the risk of heart disease and osteoporosis, when considering the risk of this treatment.

Moreover, the type of progesterone is also important, recent evidence from France suggests that while women receiving oestrogen with a synthetic progestogen have a small increase in the risk of breast cancer, this risk is not increased in women using oestrogen with the natural progesterone that is usually used today.

Conclusion

HRT has significant benefits in elevating symptoms improving quality of life reducing osteoporosis, heart disease and a reduction in overall mortality. There is no increase in the risk of breast cancer in women who have had a hysterectomy and take oestrogen alone without progesterone. There appears to be a small increase in breast cancer using combined oestrogen and progestogens, which can be minimised by using natural progesterone instead of synthetic progestogens.