Researchers in Canada and the United States are embarking on a clinical trial to see if a drug which is highly effective in treating breast cancer could be used to prevent it.

The five-year study, led by renowned breast cancer researcher Dr. Paul Goss, should answer the question of whether drugs called aromatase inhibitors (search) have a role to play in disease prevention in women after they go through menopause (search) — the time of life when three-quarters of breast cancers are diagnosed.

Goss, who is conducting a number of ongoing treatment studies with this class of drugs, said the prevention trial — launched Wednesday — was 10 years in the planning.

"For us it's the real cherry on the cake and we're very, very excited about it," he said from Boston, where he is director of breast cancer research at Massachusetts General Hospital Cancer Center.

"We're fairly sure it's going to work well too."

The trial is being co-ordinated by the National Cancer Institute of Canada clinical trials group and is funded in part by the Canadian Cancer Society.

Currently there is little that doctors can offer women who are at high risk of developing breast cancer, apart from the always sage advice to eat a healthy diet and exercise.