A study published in the British Journal of Cancer has found that the effect of combined hormone replacement therapy (HRT) in increasing a women’s risk of developing breast cancer is likely to have been underestimated in previous studies.

HRT is used to treat the symptoms of menopause (hot flushes, mood changes etc) by replacing the oestrogen that is lost during a woman’s menopause. There are two type of HRT, oestrogen only HRT and combined HRT which is mixture of oestrogen and progestogen.

Over the years studies have identified that women using HRT have an increased risk of developing breast cancer but this was only felt to be a slight increase with many stating that the benefits of taking HRT outweigh the risks.  This new study has found that combined HRT actually has a bigger effect on breast cancer risk than was previously thought.

This New Study

This new  piece of work was part of the Breast Cancer Now Generations Study which was set up in 2004 to understand the causes of breast cancer. The full Generations Study is following 113,000 women in the UK for 40 years.

 For this research into the effect of HRT, 39183 women from the Generations Study were selected who were at menopausal age. These women had  been monitored for 6 years through questionnaires which asked a number of questions including questions about their HRT use.

After the six years of monitoring it was found that 775 of the 39,183 women had developed breast cancer. Statistical analysis revealed that women using combined HRT were 2.7 times more likely to develop breast cancer than those who had not used HRT. This applied to use of HRT for a median length of time of 5.4 years and when they explored longer use of HRT, so 15+ years of use, this increased to women being 3.27 times more likely to develop breast cancer. No overall increase in breast cancer risk was observed in women who used oestrogen only HRT.

They also found that the increase in risk returns to almost normal once combined HRT use is stopped. Researchers noted that after a year and also two years of ceasing to take combined HRT there was no significant increase in breast cancer risk.

How Did Other Studies  Result in an Underestimation of Risk?

The underestimation by previous studies occurred because of the way the studies were carried out. Previous studies didn’t comprehensively follow-up with women and document their use of HRT  (e.g. did some women  stop using HRT over the course of the research) nor did they determine the age at which women went through the menopause.  These oversights caused inaccuracies.

What Does this Mean for Women Considering Taking Combined HRT?

Baroness Delyth Morgan, the Chief Executive of Breast Cancer Now said:

“Whether to use HRT is an entirely personal choice, which is why it’s so important that women fully understand the risks and benefits and discuss them with their GP. We hope these findings will help anyone considering the treatment to make an even more informed decision.

 

“On balance, some women will feel HRT to be a necessity. But in order to minimise the risk of breast cancer during treatment, it is recommended that the lowest effective dose is used for the shortest possible time.

 

“The good news is that the increased risk of breast cancer begins to fall once you stop using HRT. “If anyone is at all worried about either HRT or breast cancer, we’d highly encourage you to speak to your GP.”

The Lake Foundation believes that women considering using the combined HRT should have a discussion with their doctor about the pros and cons and make an informed decision about whether to proceed with treatment. If you can avoid combined HRT we would recommend that you do so.

You can download the full research paper below.