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

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.