Note: hormone therapy (HT) may also be referred to as hormone replacement therapy (HRT).

Background Information

The Million Women Study (MWS) is a UK national study of women's health, involving around one million women aged 50 and over. It aims to answer many outstanding questions about the factors affecting women's health in this age group. The main focus of the study relates to the effects of hormone replacement therapy use.

Comment

In the Lancet, 9 August 2003 results are reported for a study of over 1 million UK women aged 50-64 years who had provided information about their use of hormone therapy prior to a screening mammogram and were followed up for cancer incidence and death.

The study reports findings in relation to risk of breast cancer for women on combined oral therapy very similar to those of the WHI study in 2002 and 2003.

These findings provide further information about the risk of breast cancer with hormone therapies.

The authors of the Lancet study presented the following calculations:

• For 1,000 women who go through menopause aged 50 and who do not take HT, 27 breast cancers would be expected to be diagnosed by the age of 55 years.

• If the 1000 women had 5 years of combined oral HT, a total of 34 breast cancers (an extra 7 cancers) would be expected.

This is the first report of an increased risk of breast cancer for women taking oestrogen alone (oral, skin patch or implant), progesterone or tibolone.

The authors estimated that, if 1000 women took oestrogen alone for 5 years, there would be a total of 28.5 cases of breast cancer (an extra 1.5 cases per 1,000).

An increase in risk, similar to that of oestrogen only was also observed for progesterone alone and tibolone.

In a previous publication, the authors themselves have urged people to be cautious in interpreting the findings from this study. This is because the design of the study is weaker than the WHI randomised trial so the conclusions are not as reliable.

The commentary accompanying the Lancet publication describes HT as preventive therapy. This is not the current recommended use of HT. HT in Australia is prescribed for the management of symptoms that significantly impair a woman’s quality of life. Based on the findings of this study continued use for this purpose remains appropriate where the woman is fully informed about the associated risks.

Useful Resources

See also
Estrogen plus Progestin and the Risk of Coronary Heart Disease - Commentary, August 7 2003

The Jean Hailes Foundation Magazine (November 2002) Articles
Navigating the Hormone Therapy Maze

The Women's Health Initiative (WHI) results at a glance

General Information on the Women's Health Initiative  WHI Information

 Content updated August 08, 2003