Many Canadian women at high risk of breast cancer are failing to undertake preventive practices, according to a new study conducted by the University of Toronto.

It also reveals significant differences in preventive approaches among women in different parts of Canada, with women in Western Canada undertaking the most procedures and Quebec women undertaking the fewest.

Regular screening is essential for early breast cancer detection in high-risk women, says the study's author.
(CBC)

The study, published in the journal Open Medicine, tracked 657 Canadian women with a BRCA1 or BRCA2 mutation — a genetic mutation that predisposes them to a 87 per cent lifetime risk of developing breast cancer — following genetic testing.

In the study, 672 Canadian women were identified as carrying the genetic mutation following a blood test. Follow-up questionnaires were completed after a mean of four years.

Of the 342 women in the study that did not have breast cancer after four years, 157, or 46 per cent, had not undertaken any cancer prevention option, such as mastectomy, oophorectomy (removal of the ovaries), treatment with Tamoxifen, a drug that suppresses estrogen and is used to prevent breast cancer tumours, or Raloxifene, a drug that reduces the risk of hormone-positive breast cancer.

Thirty-nine per cent of the women from Ontario, 34 per cent of the women from Western Canada, and 62 per cent of the women from Quebec had not undertaken any preventive procedures.

Of the 342 women who didn't have breast cancer, 21 per cent underwent a prophylactic mastectomy, 54 per cent had a prophylactic oophorectomy, six per cent took Tamoxifen and four per cent took Raloxifene as a preventive measure.

Prophylactic mastectomy offers the greatest reduction in breast cancer risk at approximately 95 per cent. Prophylactic oophorectomy before age 40 in women with the BRCA1 or 2 mutation reduces the risk by 50 per cent. And Tamoxifen reduces the risk in high-risk women by 50 per cent.

Unsure why Quebec lags

Kelly Metcalfe, lead author of the study and an assistant professor with the faculty of nursing at the University of Toronto, told CBC.ca that the results have brought to light a serious issue.

"We can give these women their genetic testing results, tell them that they're at a significantly increased risk of developing breast cancer, but we didn't know what they were doing with that information. Now we know."

She says no one is sure why Quebec lags the rest of Canada in terms of taking preventive measures to reduce the risk of breast cancer.

"If you live in Quebec, you're much less likely to undertake any of these strategies. And that's concerning because more women in Quebec with the BRCA1 or 2 mutation will develop breast cancer, compared to women in Vancouver."

Next step: investigating causes

Metcalfe says understanding the reasons behind these regional differences form the basis of a research proposal she is currently working on.

"Our next step is to understand why those differences across the country exist. Is it because it's an access issue — are there no plastic surgeons that these women have access to? Is it not getting out the same message and information during genetic counselling, when they get their genetic test results? We're not sure why."

Metcalfe says further study is needed to determine the messages women are receiving during genetic counselling and whether the same risks and options are being presented by health-care practitioners across Canada.

She says it's incumbent on doctors to keep their patients informed about such serious and life-altering decisions as prophylactic mastectomy and oophorectomy.

"It's the responsibility of the health-care providers that are dealing with these high-risk women to keep up-to-date on this research and to be advising their patients about that research that's out there.

"Ultimately, it's up to a woman to make her decision."

For those high-risk women that adopt a watch-and-wait approach and forgo preventive measures, Metcalfe says regular screening is critical.

"Some women elect not to have these cancer prevention options but they also need to be having very regular screening and the best screening that we know of for these women is the use of MRI."

The study found that only 43 per cent of the women surveyed have been screened for breast cancer with MRI.

"We have to make sure that everybody across Canada has access to all of these options," says Metcalfe.