UK. The Million Women Study sought to examine the effect of different types of HRT and tibolone (a synthetic HRT: Livial), on the risks of breast cancer in nearly a million postmenopausal women in the UK over a period of five years. According to the Committee on Safety of Medicines (CSM), an analysis of the study results shows that

• the previously described small increase in risk of breast cancer in association with oestrogen-only products stands confirmed

• the increased risk of breast cancer in association with the use of combined (oestrogen plus progestogen) HRT is substantially higher than with oestrogen-only therapy

• tibolone (Livial) also significantly increases the risk of breast cancer, but to a lesser extent than combined HRT

• an increase in the risk of breast cancer becomes apparent within 1-2 years of starting treatment and that

• the risk of breast cancer begins to decline when HRT is stopped and by 5 years reaches the same level as in women who have never taken HRT.

The CSM advises that the benefits of short-term HRT for menopausal symptoms outweigh the risks for many women. For longer term use of HRT, women should be made aware of the increased incidence of breast cancer and other adverse effects. Each decision to start HRT should be made on an individual basis and the treatment should be reappraised regularly, at least once a year.

Reference:

1. Breast cancer and hormone replacement therapy in the Million Women Study. Lancet 2003; 362:419.

2. CSM Press Statement, 08 Aug 2003. Available from URL: http://www.mhra.gov.uk

3. ‘Dear Health Professional’ letter from Committee on Safety of Medicines, 08 Aug 2003. Available from URL: http://www.mhra.gov.uk