A Canadian researcher involved in a study that uncovered a drug capable of significantly reducing the risk of breast cancer in high-risk, postmenopausal women calls the finding a "landmark" discovery.
The American Society of Clinical Oncology announced on Saturday that a massive international clinical trial has found the drug exemestane cuts the risk of cancer for such women by about two-thirds.
Postmenopausal women with an increased risk of breast cancer, but who had not been previously diagnosed, who took part in the trial were 65 per cent less likely to contract the cancer than those who were given a placebo.
The study also found that "no serious toxicities and only minimal changes in health-related quality of life" occurred in women taking exemestane.
The findings were published in the New England Journal of Medicine on Saturday.
The trial was funded by the Canadian Cancer Society and led by Canada's NCIC Clinical Trials Group, and was known to participants as "ExCel."
Dr. Michael Wosnick, the Canadian Cancer Society's vice-president of research, said the results were extremely exciting because they had the potential to impact thousands of women.
"We know that breast cancer takes a tremendous toll on Canadian women and their families. The results of this study offer an important new option to prevent this devastating disease in women who are at higher risk for it," he told CTV News Channel on Saturday.
Wosnick said that as remarkable as the result was, it was also exciting to note that there were very few side effects aside from possible hot flashes, fatigue and joint pain.
"More importantly are the side effects that were not (found), which are cardiovascular effects, fractures and some other serious effects that come with the older class of drugs," Wosnick said.
The findings were the result of a massive international clinical trial, which included close to 250 Canadian women from 13 cities, including Vancouver, Winnipeg, Montreal, Ottawa and Toronto.
The randomized, double-blind, phase three clinical trial involved 4,560 women throughout the U.S., Canada, France and Spain over a five-year period.
Exemestane works by limiting the ability of an enzyme called aromatase to convert hormones into estrogen, which many breast cancers rely on to grow.
Wosnick says that while previous drugs were able limit the amount of estrogen in the body, exemestane ostensibly cut off the supply route at the source.
Wosniak said exemestane was already in use in thousands of women who have previously had breast cancer and are trying to prevent a recurrence.
"The logical thinking was that if a compound like this can reduce the recurrence of breast cancer, probably it can reduce the occurrence of breast cancer in the first place. That is what this new study in fact shows."
In a release issued by the Canadian Cancer Society, Vi Siemens said she and her three sisters decided to participate in the trial because their mother and two aunts had died of breast cancer.
With breast cancer running in their family, the Siemens sisters are at an increased risk of developing it themselves.
"All you have to do is look to the left or the right. Everybody knows somebody who's had breast cancer in their family. Somebody has to test these drugs," Siemens said. "You're thinking about the next generation. You'd like to do something more than in just your own corner."
Breast cancer is the most common cancer among Canadian women. The Canadian Cancer Society estimates that in 2011, 23,400 women will be diagnosed with breast cancer and 5,100 will die of it.
