Breast cancer treatment may double as preventive

TORONTO - An experimental trial to test whether a drug used in treating breast cancer can also help with prevention is now getting off the ground, and investigators are looking for Canadian participants.

More than 20,000 women were diagnosed with breast cancer last year in Canada.

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Now an experimental trial is testing if the drug Aromasin, also known as exemestane, can prevent breast cancer in women who've never had the disease.

Aromasin is one of the drugs in a new class of pharmaceuticals called aromatase inhibitors.

Typically, the medication is used to treat women with breast cancer after they've had surgery and radiation or chemotherapy. It may prevent any lurking cancer cells from growing elsewhere in the body.

It's thought that the drug works by reducing production of estrogen, a hormone that fuel the growth of tumours.

"We hope that the results will show that there's up to a two-thirds reduced risk for those women who are on this treatment," said Sarah Boulas of the Canadian Cancer Society.

The first step in the study is to test Aromasin in women who are considered to be at higher-than-average risk, such as those who have a mother or sister with breast cancer or who are simply over the age of 60.

Researchers will recruit 4,500 women in Canada, the U.S. and Spain. Half will take Aromasin, the others a placebo.

Redesigned study

Originally, those taking Aromasin in the breast cancer prevention trial were also supposed to take the anti-inflammatory Celebrex. After a similar drug, Vioxx, was pulled from the market for causing heart attacks, and warnings were strengthened for Celebrex, researchers decided the anti-inflammatory might dissuade women from participating in the trial and the experiment was redesigned.

All participants will be monitored for possible side-effects of the drug, such as bone loss and dementia.

The study's lead investigator, Dr. Paul Goss of Massachusetts General Hospital in Boston, doesn't anticipate a day when every woman will take a pill to prevent breast cancer.

"Our belief and hope is that at the end of this trial we will have demonstrated not just that our drug can prevent breast cancer, but in whom it most likely will work," said Goss.

Aromasin is not the first drug to be tested for the prevention of breast cancer. Tamoxifen is approved for this use in the U.S., but not in Canada or Europe, because of concerns it increases the risk of endometrial cancer and strokes.

The results of the Aromasin trial aren't expected until 2010.