"We asked the women in our study group what they thought their risk of developing breast cancer was on a scale of zero to 100 per cent," says Professor Kelly Metcalfe of nursing at U of T and lead author of a paper in the Oct. 16 issue of the Journal of the National Cancer Institute. "Looking at all the 75 women in the study, 30 per cent of them estimated their risk to be 100 per cent. We don't even allot that level of risk to women who carry a mutation in one of the two breast cancer susceptibility genes. The highest risk we would give is 80 per cent. So these women's risk estimates were very elevated, particularly for those who did not carry the genetic mutation."

Prophylactic bilateral mastectomy is a preventative option for women who are at high risk of developing breast cancer. From 1991 to 2000, Metcalfe - who did this work as part of her PhD thesis - and Dr. Steven Narod of the Centre for Research in Women's Health at Sunnybrook and Women's College Health Science Centre and the University of Toronto attempted to contact all the women in Ontario who had prophylactic bilateral mastectomies.

The researchers identified about 120 women; 75 agreed to take part in the study. The women provided detailed family histories of the number and type of cancers within their family and the ages of onset. With that information, they determined an objective risk estimate for each woman and the likelihood of developing breast cancer. "We wanted to compare the perceptions of breast cancer risk among women with objective estimates of what their risks actually were," says Metcalfe.

The researchers found that all the women in the study significantly overestimated breast cancer risk except those who carried the mutation of the breast cancer susceptibility genes, BRCA
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Contact: Janet Wong
jf.wong@utoronto.ca
416-978-5949
University of Toronto
15-Oct-2002