Drug 'boosts breast cancer fight'

The drug is currently given to women with advanced breast cancer

Many women who are being treated for breast cancer could benefit from taking another drug, a study suggests.

Most women with breast cancer take a drug called tamoxifen for up to five years to reduce the risks of the disease coming back.

But a study of 4,742 women suggests switching to a drug called exemestane after two or three years may be better.

Writing in the New England Journal of Medicine, doctors said it cuts the risks of recurrence by one third.

The BBC's Vicky Young

Risks reduced

Tamoxifen is the drug of choice for most women who have had breast cancer.

Studies have shown it can reduce the chances of the disease returning by 47% and the risk of death by 26%.

It's essential that we continue to study the drug to make sure it doesn't expose patients to any unpredicted long-term risks

Professor Robert Souhami,
Cancer Research UK

However, some women can become resistant to tamoxifen. Others can suffer potentially serious side-effects.

This latest study, which involved women from 37 countries, examined whether switching to exemestane could benefit these patients.

Exemestane is licensed in the UK. However, at the moment it is only given to women with advanced breast cancer who won't benefit from surgery.

All of the women involved in the study had been taken tamoxifen for between two to three years.

They were divided into two groups. One continued taking tamoxifen while the other took exemestane.

Doctors found that those on exemestane were less likely to see the disease return. For every 100 patients, who took the drug, eight had a recurrence within three years.

This compares to those on tamoxifen. For every 100 patients on this drug, 13 had a recurrence within three years.

"Though recurrence of breast cancer in women taking tamoxifen was already low, our results show that switching to exemestane can reduce that number by about a third," said Judith Bliss of Cancer Research UK, one of the study authors.

Doctors also found that taking exemestane reduced the risks of developing cancer in the other breast or in the uterus.

"Women switching to exemestane had fewer cases of cancer in the other breast, which also suggests that taking the drug after tamoxifen may be a better way to prevent breast cancer than taking tamoxifen alone," said Professor Charles Coombes of Imperial College London, the study's lead author.

Switching drugs

Doctors said switching to exemestane, which is manufactured by Pfizer, could help to avoid these potential problems.

However, they warned that further research is needed to find out exactly when women should switch from tamoxifen to exemestane. They will also need to examine the long-term effects.

"While this is good news, it's important to remember that these results only tell us what happens in the short term," said Professor Robert Souhami, director of clinical and external affairs at Cancer Research UK.

"It's essential that we continue to study the drug to make sure it doesn't expose patients to any unpredicted long-term risks."

Delyth Morgan, chief executive of Breakthrough Breast Cancer, said: "While this trial is extremely promising, the results are only preliminary and the trial needs to continue before the long-term effectiveness and side effects of the drug are established."