The Breast Cancer Society of Canada

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Hereditary Breast Cancer: When should you get tested?

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In response to Angelia Jolie’s decision to undergo a double mastectomy, our organization has been inundated with phone calls from news stations and questions from the general public. I want to inform our supporters and the public about hereditary breast cancer to help all women make wise and educated decisions about their personal health care.

First of all, let’s understand what heredity is and why it is important to breast cancer. A family history of breast cancer can be an important risk factor because of heredity. We inherit packages of information, called genes, from our parents. We inherit one copy of each gene from our mother and one copy from our father.

If an abnormal change, known as a mutation, occurs in one of the two copies of a gene, it prevents that gene from working properly which can eventually produce uncontrolled cell division. This mutation together with other factors could cause a cell to develop into cancer after many years.

A mutation can 1) occur by chance in a single cell, or 2) be inherited from either parent. Women who are at risk for hereditary breast cancer may have inherited a mutation which increases their breast cancer risk.

That brings us to the next major question- what is hereditary breast cancer? BRCA1 and BRCA2 (BReast CAncer 1 or 2) are the two most important known genes which can have a mutation that:

  • Greatly increases the risk of breast cancer (In Jolie’s case it was increased to 87%)
  • Increases the risk of ovarian cancer
  • Can be inherited from either one’s mother or father
  • Has a 50% chance of being inherited if a parent carries that mutation because the mutation is present in only one of the two copies of the gene. A person who has not inherited a mutation from either parent cannot pass it on to his or her children

Genetic evaluation always includes a detailed assessment of family history and genetic counselling. It may include a blood test for gene mutations. These tests DO NOT tell whether or not a woman has breast cancer, but may determine whether she has inherited a BRCA1 or BRCA2 mutation. Many women who inherit a breast cancer gene never develop breast cancer.

It is important to remember that only 1 in 20 case of breast cancer is due to an inherited gene. Breast cancer is a common disease but hereditary breast cancer is not common.

Things to look out for that may suggest hereditary breast cancer:

  • Three or more relatives on the same side of the family with breast or ovarian cancer
  • Two or more closely related relatives on the same side of the family with breast or ovarian cancer. (Closely related female relatives: mother, daughter, sister, grandmother, aunt, niece)
  • A closely related relative diagnosed with breast cancer before age 50
  • A closely related relative with ovarian cancer
  • A closely related relative with cancer in both breasts or both breast and ovarian cancer
  • A closely related relative of Jewish ancestry with breast or ovarian cancer
  • A closely related male relative with breast cancer

The personal decision….
Lowering breast cancer risk can come with sacrifice. In Jolie’s case, it meant major surgery and months of recovery time. For women with extremely high risk of breast cancer, surgical removal of the breasts (risk reduction mastectomy), with or without reconstruction is an option that could reduce breast cancer risk by over 90 per cent. Certain drugs, such as tamoxifen, raloxifene, or aromatase inhibitors taken over a five year period have been shown to reduce risk in some women.

Jolie’s decision to reduce her risk for breast cancer by opting for the surgical removal of her breasts was a bold move; albeit a very personal decision. Her prominence in the entertainment world brings this topic to the forefront yet again. Everyone needs to be well informed of the details of hereditary breast cancer and the options available to make an informed decision for themselves.

What to consider before visiting your doctor

Marsha Davidson

Executive Director
Breast Cancer Society of Canada

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