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Breast cancer Q&A with Dr. Ruth Heisey: The most important history lesson



Dr. Ruth Heisey
Dr. Ruth Heisey

The following Q&A features Dr. Ruth Heisey, medical director of The Peter Gilgan Centre for Women’s Cancers at Women’s College Hospital, in partnership with the Canadian Cancer Society. Breast cancer is the most common cancer found in Canadian women, affecting around 1 in 9. While we don’t know what causes most cancers, around 5-10 per cent of breast cancers are caused by hereditary factors where genetic mutations are passed down through families, which is why knowing your family history matters.

1) What does the research say about the link between a person’s family history and their chances of developing breast cancer one day?
Women who have a first degree relative with breast cancer (i.e. their mother, sister or daughter) have a two-fold increased risk of developing breast cancer in their lifetime. If that relative had her cancer diagnosed before menopause, the risk increases to three-fold.

Women should definitely find out if there are any first degree relatives who have been diagnosed, but second degree relatives (i.e. aunts, nieces or grandparents) with a cancer diagnosis are also important - particularly if it was diagnosed at a young age.

2) When should a woman start looking into their family history?
All women should know their family history - it could be life-saving. Women with a strong history of breast and/or ovarian cancer might be candidates for genetic testing or enhanced screening starting as young as 25-30 years of age.

3) Is it as important to look on our father’s side of the family as it is on our mother’s side?
The short answer is yes. The most common hereditary breast cancers occur in families that carry a BRCA1 or BRCA2 genetic mutation. These mutations are passed down in an autosomal dominant fashion, which means that each relative has a 50 per cent chance of carrying the mutation once it has been identified in a family. If the carrier is male, he may never develop breast cancer, so it may be less obvious that the family has a mutation.

4) Is there a connection between breast and ovarian cancer when we look at family history?
Women in families with BRCA mutations have substantially increased risks of developing not only breast cancer, but also ovarian cancer, for which we have no effective early detection strategy. These cancers tend to present at an earlier age and are more common in families that are of Ashkenazic Jewish background.

If we identify a mutation carrier and that woman chooses to have her ovaries removed after she finishes having her children, we may prevent her from developing ovarian cancer. While offering risk-reducing breast surgery may end up preventing breast cancer, for women who decide against surgery, enhanced screening annually with an MRI in addition to mammography may help with early detection.

5) What is considered to be a “strong” family history of breast cancer?
Having a strong family history of breast cancer means that someone would have to have multiple relatives diagnosed with either breast and/or ovarian cancer, particularly before menopause. Any family that includes a man with a history of breast cancer may also carry a mutation.

6) What should women do if they have a strong family history?
Make sure that your healthcare provider knows your history. Ask your doctor if you should have genetic testing and/or enhanced screening with MRI in addition to mammography. Ask if you should start having your mammograms at age 40. Women who are not genetic mutation carriers still might be at sufficiently increased risk to warrant high-risk screening because breast cancer is still found in families that do not carry these known genetic mutations. In research, we are still exploring whether there are other factors that contribute to risk. 

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  • Women's College Hospital