Women taking combined hormone replacement therapy (HRT) are 2.7 times more likely to develop breast cancer than non-users, and the risk may increase with longer use, a study published in the British Journal of Cancer has found. Those taking oestrogen-only HRT did not have an increased risk, the study found.

The findings were drawn from thousands of women taking part in the Breast Cancer Now Generations Study – a major study following more than 100,000 women for 40 years to investigate the causes of breast cancer.

Experts analysed data over six years from almost 40,000 menopausal women, 775 of whom developed breast cancer.

The current study included 39,183 women with a known menopausal age who were followed for more than six years. Of these, 1,719 women were current users of oestrogen-only HRT, 1,612 were current users of combined HRT, and 398 were current users of some other form of HRT, mainly tibolone. Of the sample group, 20,114 women had never used HRT and 5,771 women were former users.

After adjusting for current age, menopause age, and other factors, women taking oestrogen plus progesterone HRT for a median of 5.4 years were found to be 2.7 times more likely to develop breast cancer than those with no previous HRT use – this translates into a hazard ratio of 2.74.

The risk increased to 3.27 in women who had taken combined HRT for 15 years or more. However, the study found no increased risk of breast cancer in women using oestrogen-only HRT.

“Like all medication, there are potential side effects and this is why care, counselling and supervision in the use of any medication including HRT is important” – Mark Brincat, head of obstetrics and gynaecology at Mater Dei Hospital. Photo: Alan Carville

The researchers also found that women’s increased risk level returned to normal once they stopped taking combined HRT, confirming the findings of previous studies.

HRT is used to treat symptoms of the menopause – such as hot flushes, migraines, disrupted sleep, mood changes and depression – by replacing hormones lost through the menopause.

“The epidemiological publication referred to adds nothing new to what had been published in the Women’s Health Initiative (WHI) over 15 years ago, namely that women on a particular combination of HRT, the combined one, had numerically a small number of cases of breast cancer higher than women on no treatment,” said Mark Brincat, head of obstetrics and gynaecology at Mater Dei Hospital.

The researchers, from the Institute of Cancer Research in London, said that previous studies may have substantially underestimated the risk of breast cancer from combined HRT, as they did not update information about a woman’s HRT use or analyse accurately to allow for her age at menopause.

HRT is a very important therapeutic manoeuvre in women’s health

“Though important, the actual number remained small and was a statistical, not necessarily a causative increase. WHI was prospective and we have moved on considerably in the field of HRT since then,” continued Brincat.

“Indeed the advice from the Royal College of Obstetricians and Gynaecologists (RCOG), and Breast Cancer Now, as reported in the British Journal of Cancer, despite this current paper remains exactly the same, and in no way condemns HRT, just advocating its judicious use, just like with any other form of medication.

“It is only the combined preparation with certain progestogens that statistically increases the risk, once again given in increased rates rather than numbers. The oestrogen only HRT on its own, that is frequently used, does not. The actual numbers are small at any rate and nobody is sure whether this is a direct effect or not.

“HRT is a very important therapeutic manoeuvre in women’s health and confusion on breast cancer a very common occurrence,” said Brincat.

Referring to an article published in The New York Times on Thursday (Rethinking The Use Of Hormones To Ease Menopause Symptoms), Brincat explained that what is however more certain is the beneficial effects of HRT, both combined or oestrogen only.

“Combined is protective against cancer of the lining of the uterus. In cases of women with a hysterectomy, no progestogen is needed; therefore there is no need for combined HRT, but oestrogen only,” he said.

The American paper reported research suggesting that the benefits of short-term hormone treatment to control life-disrupting menopausal symptoms outweigh the risks – as long as the treatment is started at or near menopause.

Advantages that have been well studied include relief of hot flushes, relief of joint aches and pains, bladder and concentration improvements among others.

“Long-term health benefits include skin, bone strength, prevention of Alzheimer’s and reduction in heart attacks and stroke. Above all is an improvement in quality of life and mobility. Quality of life not simply quantity matters.

“The unnecessary avoidance of HRT has had a major impact on women’s health over the last 16 years. This not only did not reduce the incidence of breast cancer in some cases, but in certain countries there was an increase in incidence – such is the nature of the disease with the many, many factors that seem to influence its incidence.

“Advantages that have been well-studied include relief of hot flushes, bladder and concentration improvements among others.

“Health benefits include long-term ones such as skin health, bone health, muscle and joint benefits, and also very likely benefits to the cardiovascular system and prevention of dementia.

“Used properly this is a useful tool.”

Brincat said that, like all medication, there are potential side effects and this is why care, counselling and supervision in the use of any medication including HRT is important.

“In concentrating repeatedly on the rare side effects of a particular form of HRT, the health benefits of HRT in appropriate women are however very convincing and HRT has a long 70-year history of use, giving tangible benefits to millions of women that cannot be ignored, and for which many women due to poor selection, sweeping generalisations or poor education have been deprived of.”