The Pharmaceutical Journal
Vol 268 No 7191 p419-425
30 March 2002

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Third European Breast Cancer conference in Barcelona (more)

Tamoxifen prevents breast cancer, but are side effects outweighing benefits?

Use of tamoxifen as a preventive measure in healthy women at high risk of breast cancer reduces the incidence of the disease by a third, researchers say. However, they are unable to conclude whether the benefits of tamoxifen outweigh its side effects, such as thromboembolism, in these women.

In an international study of 7,000 women at increased risk of breast cancer who were assigned to receive either tamoxifen or placebo, the researchers found that 68 of the women treated with tamoxifen developed breast cancer compared with 101 of the women taking placebo. The benefit of tamoxifen was the same irrespective of the woman's age, the level of risk or whether she was taking hormone replacement therapy or not.

Lead researcher Professor Jack Cuzick of Cancer Research UK commented that by taking tamoxifen the number of deaths from breast cancer within 10 years of diagnosis in women at high-risk may be reduced by 18 per cent.

However, there was, in line with the findings from other tamoxifen trials, a two- to three-fold increase in the risk of endometrial cancer and a two- to three-fold increase in the risk of thromboembolism in women taking tamoxifen.

In the trial, 40 per cent of blood clots occurred within three months of surgery or following immobility. Professor Cuzick said that it is essential to continue to follow the participants to see if a particular group of healthy high-risk women can be identified for whom the benefits of tamoxifen clearly outweigh any risks."

Four women in the trial died from breast cancer, two in the tamoxifen group and two in the placebo group.

Professor Gordon McVie, joint director general of Cancer Research UK, emphasised that women with breast cancer who are being treated with tamoxifen should continue to do so and that the benefits of taking tamoxifen as a treatment outweigh potential side effects.

These preliminary results of the International Breast Cancer Intervention Study, funded by Cancer Research UK and the Department of Health, were presented at the third European Breast Cancer conference in Barcelona, last week, following a recommendation by the trial's independent data monitoring committee.