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Trial team: Professors Mitch Dowsett (left), Ian Smith and Trevor Powles


women took part in the trial

Thirty years ago, The Royal Marsden started a cancer prevention study of the drug tamoxifen, which has become one of the most important trials ever to be carried out at the hospital. The results showed that the drug, which blocks oestrogen, considerably reduces the risk of women developing ER+ breast cancer.

The trial’s lead investigator was Consultant Medical Oncologist Professor Trevor Powles, who was also Head of the Breast Unit before his departure in 2003. In 1986, he enrolled 2,471 women – who were all at high risk of developing breast cancer – onto the trial. The women were randomly chosen to take either tamoxifen or a placebo daily for eight years. They also had a clinical review every six months and a mammogram every year.

This is still considered the largest single-centre preventative trial ever to be carried out in the UK. After 20 years, the results showed that overall invasive breast cancer rates were not statistically different between the two groups of women. But when researchers looked at ER+ breast cancer, the results showed that women who took tamoxifen reduced their risk of developing the disease by 39%.

Professor Ian Smith, a Consultant Medical Oncologist at The Royal Marsden who worked with Professor Powles on the trial, said: “This groundbreaking trial led the world’s attempts to prevent breast cancer developing in  healthy women who were deemed at risk.”

Women who took tamoxifen reduced their risk of developing the disease by 39%

A patient's perspective

Kaeti Warder, trial participant

“I was referred to The Royal Marsden because of my family history: my grandma and mother both had breast cancer. I was asked to consider going on the tamoxifen trial. I agreed, and never looked back!

“I was treated incredibly well, with frequent checkups and mammograms, and any concerns were dealt with. We had ‘get-togethers’ between staff and patients, which were very reassuring.

“I’m delighted to have been part of this trial and hope that the results will help many other women now and in the future.”