A trial looking at anastrozole to prevent breast cancer in postmenopausal women (IBIS II Prevention)

Cancer type:

Breast cancer

Status:

Results

This trial looked at whether a drug called anastrozole could reduce the risk of breast cancer in post menopausal women who are at a high risk of getting the disease. The trial was supported by Cancer Research UK.

The female hormone oestrogen can encourage breast cancer cells to grow. Drugs called aromatase inhibitors Open a glossary item can stop the body making oestrogen, which may help to prevent breast cancer.

Anastrozole is an aromatase inhibitor that doctors can use as a treatment for breast cancer in women who have been through the menopause Open a glossary item (post menopausal women).

Researchers wanted to see if anastrozole could also help to prevent breast cancer in post menopausal women who were at high risk of getting the disease. In this trial, some women took anastrozole, and some took a dummy tablet (a placebo Open a glossary item).

Trial results

The researchers found that taking anastrozole for 5 years reduced the number of breast cancers in post menopausal women who were at high risk of getting the disease.

The trial recruited nearly 4,000 women who had been through the menopause and were considered to be at high risk of getting breast cancer. This was generally because they had a strong family history of breast or ovarian cancer. Or because they’d had LCIS or DCIS, or certain types of high risk benign breast disease.

This was a randomised trial. The women taking part were put into treatment groups by a computer. Neither they nor their doctor could decide or knew which group they were in. This is called a double blind trial.

  • 1,920 women took anastrozole every day for 5 years
  • 1,944 women took a dummy drug (placebo) every day for 5 years

After monitoring the women for an average of 5 years, the researchers looked at the number of women who had developed breast cancer. They found this was

  • 40 women in the group taking anastrozole
  • 85 women in the group taking the dummy drug

The researchers will follow the women for longer to see if the effect of taking anastrozole lasts and to monitor any side effects

The side effects that women had were similar in both groups. But more women taking anastrozole had problems such as joint pain or stiffness, hot flushes and dry eyes.

The trial team concluded that anastrozole can reduce the risk of breast cancer in post menopausal women who are at high risk of the disease.

We have based this summary on information from the team who ran the trial. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team. We have not analysed the data ourselves.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Professor Jack Cuzick
Professor John Forbes
Professor Anthony Howell

Supported by

AstraZeneca
Cancer Research UK
Experimental Cancer Medicine Centre (ECMC)
NIHR Clinical Research Network: Cancer
Queen Mary University of London
Sanofi Aventis

Other information

This is Cancer Research UK trial number CRUK/04/032/033.

Contact our cancer information nurses for other questions about cancer by:

Phone - 0808 800 4040

Last review date

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Deborah wanted to help other breast cancer patients in the future

“Deborah agreed to take part in a trial as she was keen to help other cancer patients in the future. "If taking part in a trial means others might be helped then I’m very happy with that."

Last reviewed:

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