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Breast Health

Are you High Risk

Understanding Your Risk of Breast Cancer

There’s a lot of chatter about breast cancer risk, but what does it all really mean? It’s important first to understand the concept of “risk” and know about breast cancer risk factors.

Young women have a tendency to overestimate their risk for developing breast cancer. Most people have heard the statistic that says 1 in 8 women will develop invasive breast cancer. Many young women misinterpret this to mean that, on any given day, they and the women they know have a 1-in-9 risk of developing the disease.

In reality, about 1 in 9 women — 12.5%, or about 12.5 out of every 100 — can expect to develop breast cancer over the course of an entire lifetime. In Canada, an average lifetime for women is about 90 years. So, it’s more accurate to say that 1 in 8 women in Canada who reach the age of 90 can expect to develop breast cancer.

As for your risk as a young woman, 5% of breast cancer diagnoses will be women under 40.

Don’t panic! Having several risk factors does not mean you will get breast cancer. It just means that your chances of getting the disease are higher than those who have fewer risk factors. Read on to understand risk, then speak with your doctor to determine your personal risk level and develop an appropriate plan for you.

Factors that may put you at High Risk for Breast Cancer

(Women with a high risk have a 30% or greater chance of developing breast cancer in their lifetime, or at this level of risk, 300 or more women in every 1,000 will develop breast cancer.)*

Genetic factors: Over the past decade, two breast cancer susceptibility genes have been discovered and characterized: BRCA-1 and BRCA-2 (also sometimes referred to as the “Angelina Jolie genes” if you’re a pop culture buff). Certain inherited mutations (changes) in either of these genes will increase a woman’s risk of developing breast and ovarian cancer. Still, those with a well-documented genetic predisposition to breast cancer only account for 5%-10% of cases diagnosed. Women who carry a mutation in their BRCA 1 or BRCA 2 genes have a 40%-85% chance of developing breast cancer in their lifetime, are more likely to develop breast cancer at a younger age (before menopause), and often have multiple family members with the disease. Although the BRCA genes are the most significant in influencing breast cancer risk, there are other genes that have been discovered that may increase your risk as well. If you are concerned about your genetic risk, talk to your doctor to learn more about your eligibility for genetic testing.

Family History: Most women who have breast cancer do not have breast cancer in their family history. However, women with close relatives who’ve had breast cancer have a higher risk of developing the disease themselves. If you’ve had one first-degree female relative (sister, mother, daughter) diagnosed with breast cancer, your risk is doubled. It is also important to know your family history of cancer on your father’s side too. If you’re unsure about your family’s medical history – ask!

Exposure to Radiation: Women who have undergone radiation treatment to the chest, neck and armpit area are at higher risk for breast cancer. This risk factor is particularly evident in women who were treated for Hodgkin’s lymphoma when they were younger. If you were treated with radiation before age 30, chat with your doctor about your potential risk.

Click here to learn more about the resources available to women at high risk for breast cancer.

Factors that may put you at Moderate Risk for Breast Cancer

(Women with a moderate risk have a lifetime risk of developing breast cancer of greater than 17% but less than 30%. Or for this level of risk more than 170 but fewer than 300 women in every 1,000 will develop breast cancer.)*

Personal History: You have an elevated risk of developing breast cancer if:

  • You have a personal history of breast or ovarian cancer
  • You had a previous breast tissue biopsy showing abnormal cells
  • You have high bone density
  • You are shown to have dense breast tissue on a mammogram

Hormonal Factors: Some of the factors that may increase your risk for breast cancer are hormonal and related to a woman’s reproductive history. The greatest risk results from breast tissue being consistently exposed to estrogen, as it is through long periods of uninterrupted menstrual or ovulatory cycles. Hormonal factors that increase risk include:

  • Birth of a first child after the age of 30 or not having children at all
  • Menstruation starting at an early age (before 12)
  • Late menopause (after 55)
  • Taking birth control pills and/or hormone replacement therapy (although debated, many experts say that this slightly increases one’s risk)

Lifestyle Factors: Evidence shows lifestyle factors that increase estrogen levels can increase your risk of developing breast cancer:

  • Drinking alcohol, including low levels of alcohol consumption (alcohol may raise estrogen in the blood)
  • Obesity with excess caloric and fat intake (fatty tissue may raise estrogen levels)
  • Sedentary lifestyle – women who exercise regularly are at lower risk for breast cancer than those who do not.

Emerging Risk Factors: In addition to known, established risk factors, on-going research is identifying newly suspected risk factors. Many pollutants in the environment have biological effects. Even in the absence of concrete evidence linking these chemicals to breast cancer or other diseases, it is not safe to assume they are benign. As a precautionary principle, avoiding whenever possible—especially in early life in the womb and in adolescence when breasts are rapidly growing—is prudent. Emerging risk factors include: Low level of Vitamin D Light exposure at night, chemicals in food and water, chemicals in cosmetics and personal care products, chemicals in plastic, night shift work, tobacco smoke, red meat intake. Although it may seem that there are many risk factors for getting breast cancer, there are also several things you can do to lower that risk.

High Risk Project

The High Risk Breast Cancer Project is a collaborative effort between four leading breast cancer organizations: The Canadian Breast Cancer Foundation, Ontario Region; The Canadian Breast Cancer Network; Rethink Breast Cancer; and Willow Breast & Hereditary Cancer Support. The High Risk Breast Cancer Project aims to respond to the needs of Canadians who are at an elevated risk of developing breast cancer through targeted activities that seek to increase awareness, provide support tools, and build community for high risk women and their families. Click here to learn more about the resources available to women at high risk for breast cancer.


*National Institute for Health and Care Excellence (NICE)