September 19, 2014
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Breast Cancer

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Genetic testing

Can you really inherit cancer?

In parts of North America, hereditary cancer syndromes may be responsible for up to 10% of all cancer cases. People affected by such syndromes have up to a 90% lifetime risk of developing cancer, often diagnosed at young ages.

Breast, ovarian, and colon cancers

The genes responsible for hereditary breast and ovarian cancers are BRCA1 and BRCA2. The genes that carry hereditary colon cancer are MSH2, MLH1, PMS1, and PMS2. Their relatively recent discovery provides doctors not only with the opportunity to identify the family members who have inherited these particular gene mutations, but also to offer appropriate clinical interventions to aid in the prevention, early detection, and treatment of these cancers. Family members who have negative results on these tests may be spared ongoing scrutiny and anxiety.

Should you be tested for genetic cancer syndromes?

Genetic risk assessment may be appropriate if you are:

  • A woman with breast cancer diagnosed at age 35 or younger.
  • A woman with ovarian cancer diagnosed at age 50 or younger.
  • An Ashkenazi Jewish woman with breast or ovarian cancer diagnosed at any age.
  • A man or woman with colon cancer diagnosed at age 50 or younger.
  • A blood relative with a confirmed mutation of a cancer susceptibility gene.

  • Examples:
    • BRCA1, BRCA2 for hereditary breast or ovary cancer
    • MLH1, MSH2 for hereditary nonpolyposis colon cancer (HNPCC)
    • APC for familial adenomatous polyposis (FAP)

Or whose family history includes any 2 of the following:

  • Cancer in 2 or more closely related family members such as parents, siblings, children, grandparents, aunts, or uncles on the same side of the family.
  • Cancers at an earlier age than expected in the general population. For example, breast cancer before menopause or colon cancer before age 50.
  • Multiple primary cancers in one individual.
  • Cancers associated with known hereditary syndromes such as breast/ovary or colon/uterus cancers.
  • Male breast cancer.

Other hereditary syndromes with a very high risk for prostate cancer, malignant melanoma, and other tumours are the subjects of intensive study, and the genes responsible will soon be identified. These discoveries will provide new opportunities and challenges for cancer prevention and treatment.

It is important to discuss your options with a genetic counsellor before having genetic testing done so that you are informed of all of the benefits and consequences of the test. It may also be a good idea to talk to other women who have had genetic testing done to see how it has affected their lives.

If you test positive for one of the breast cancer genes, there are several options for decreasing your chances of developing breast cancer, if you should choose to do so, including closer screening, surgery, hormonal therapy, or lifestyle changes. These options are discussed in the next section.

 
Adapted from the Cancer Management manual 
published by the BC Cancer Agency, 
in association with Dr. Michael Pezim, MD 
and the MediResource Clinical Team 

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