A trial looking at the long term benefits of taking tamoxifen for 5 years after breast cancer surgery

Cancer type:

Breast cancer

Status:

Results

Phase:

Phase 3

This trial compared taking tamoxifen for 5 years after breast cancer surgery with taking it for just 2 years. It was for women over 50 years of age. This trial was supported by Cancer Research UK.

After surgery for early breast cancer, many women have a hormone therapy drug called tamoxifen.

Doctors knew from research that taking tamoxifen helped to reduce the risk of breast cancer coming back. But in this trial, researchers compared 5 years of tamoxifen with just 2 years.

The aim of the trial was to see if taking tamoxifen for 5 years reduced the risk of breast cancer coming back more than 2 years of treatment.

Summary of results

The trial showed that women who took tamoxifen for 5 years had a lower risk of breast cancer coming back than women who took it for just 2 years.

The trial recruited 3,449 women in a number of European countries. They had all had surgery to remove breast cancer. Just over half of them (52%) had been through the menopause.

After taking tamoxifen for 2 years, the women were put into 1 of 2 treatment groups. Neither they nor their doctor could decide which group they were in. This is called randomisation.

  • 1,724 stopped taking tamoxifen after 2 years
  • 1,725 went on to take tamoxifen for another 3 years (5 years treatment in total)

The trial team followed up the women for an average of 10 years. They found that 10 years after starting treatment, cancer had come back or developed in the other breast in

  • 589 women who took tamoxifen for 2 years
  • 514 women who took it for 5 years

They also found that taking tamoxifen for 5 years reduced the risk of heart disease. This effect was strongest for women aged between 50 and 59.

The researchers concluded that the results show taking tamoxifen for the full 5 years reduced the risk of breast cancer coming back. It also lowered the risk of heart disease. They suggest that women should be encouraged to complete the full 5 years of tamoxifen treatment.

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) 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 Michael Baum

Supported by

Cancer Research UK

Other information

This is Cancer Research UK trial number CRUK/86/001.

Questions about cancer? Contact our information nurses

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle 8053

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

Harriet wanted to try new treatments

A picture of Harriet

“I was keen to go on a clinical trial. I wanted to try new cancer treatments and hopefully help future generations.”

Last reviewed:

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