One in nine Canadian women is expected to develop breast cancer during her lifetime. That’s a striking statistic. But what does it mean to you?
In this section, the Canadian Breast Cancer Foundation helps you navigate the topic of breast cancer risk with statistics and evidence-based facts that can help to inform your decisions about taking action to reduce the risk of breast cancer.
Breast cancer incidence increases with age
Canadian cancer statistics have been gathered over time and from across Canada. They give us part of the picture of how breast cancer affects lives in Canada. Statistics show us how breast cancer incidence (the number of new cases) increases with age. The following are estimates for 2011:
965 breast cancer cases diagnosed in women under the age of 40
3,500 breast cancer cases diagnosed in women 40–49
6,300 breast cancer cases diagnosed in women 50–59
6,200 breast cancer cases diagnosed in women 60–69
6,500 breast cancer cases diagnosed in women 70+
In 2011, an estimated 190 men in Canada will also be diagnosed with breast cancer. Men with breast cancer make up a little less than one percent of all breast cancer cases.
Assessing your risk by risk factors
A risk factor is something that increases a person’s chance of developing a disease.
Established risk factors for breast cancer are backed up by a body of research with conclusive evidence that is confirmed by different sources and studies. Risk factors are associated with an increased risk of breast cancer. This means that they have been linked to the development of the disease.
While risk factors are established by conclusive research, they cannot be seen as rules or guarantees. Even if you have several risk factors for breast cancer, this does not mean you will develop the disease. On the other hand, some women who are diagnosed with breast cancer have no identifiable risk factors other than being a woman. This tells us that there’s much more to be discovered about breast cancer, its causes, and what we can do to reduce the risk.
Understanding how risk factors increase breast cancer risk
Some breast cancer research explores how different risk factors influence the development of breast cancer. This can help us better understand its causes and how to help prevent it. Breast cancer is a complex disease with many factors that interact in ways we don’t fully understand.
In your own life, knowledge of risk factors can help you to put your own risk of breast cancer into perspective, encourage you to learn more, or motivate you to take action to reduce your risk. To inform your decision making, you may also find it helpful to speak to a health care provider.
Understanding relative risk factors
The following table is a list of some of the established risk factors for breast cancer. All of these factors increase a person’s risk of developing breast cancer, with some carrying more weight or a higher risk than others. Being female and ageing are the strongest risk factors. Other risk factors are given with an estimate for how many times greater the risk is for someone who has the risk factor over someone who does not have it, all other factors being equal.
The Canadian Breast Cancer Foundation encourages you to use this information to think about breast cancer risk in terms of relative risk factors and lifestyle changes that can help to reduce your breast cancer risk. To further inform your understanding, we encourage you to consider speaking with a health care provider.
High risk = a factor that increases a person's breast cancer risk by 3 times or more
Example: having had lobular carcinoma in situ (LCIS) leads to a 7-10 times greater risk than a person who has not had LCIS.
Moderate risk = a factor that increases a person's breast cancer risk by 1.5–3 times
Example: starting menopause later than age 55 leads to a 2 times greater risk than a woman who started menopause younger than 55.
Lower risk = a factor that increases a person's breast cancer risk by 1-1.5 times
Example: being an unhealthy body weight leads to a 1-1.5 times greater risk than a person who is a healthier weight.
SELECTED RISK FACTORS FOR BREAST CANCER |
| Moderate-to-high risk factors |
Established Risk Factors |
Effect on Breast Cancer Risk* |
Ageing |
Very strong increase in risk |
Being female |
Very strong increase in risk |
Lobular carcinoma in situ (LCIS) |
7–10 times greater |
BRCA 1 or BRCA 2 gene mutation |
5–14 times greater |
Clinically diagnosed high breast density |
3–6 times greater |
Family history of breast cancer
- 2 immediate family members with breast cancer
- Mother diagnosed before age 60
- Mother diagnosed after age 60
|
3–4 times greater
2–3 times greater
1 times greater |
Radiation exposure or frequent X-rays to the chest before the age of 30
- Risk for breast cancer diagnosed at age 40
- Risk for breast cancer diagnosed at age 60
|
11 times greater
3.5 times greater |
Personal history of cancer (including breast cancer, DCIS, Hodgkin’s disease and other cancers) |
2–6 times greater |
Benign breast condition (hyperplasia)
|
2–4 times greater
1.5–2 times greater |
| Lower risk factors |
| Modifiable risk factors |
HRT use (current or recent use for 5+ years)
- Combined estrogen and progestin
|
1.5–2 times greater |
| Using birth control pills (current or recent use) |
1–1.5 times greater |
| Not having children (compared with a woman who has her first child before 35) |
1.5 times greater |
| Alcohol consumption (2–4 drinks per day) |
1.5 times greater |
| High socio-economic status |
1–2 times greater |
| Being an unhealthy body weight |
1–1.5 times greater |
| Not breastfeeding |
1 times greater |
| Lack of exercise |
1 times greater |
| Non-modifiable risk factors |
| High bone density |
2 times greater |
Age 55 or older at menopause |
2 times greater |
First period before age 12 |
1–1.5 times greater |
Being tall |
1 times greater |
Ashekenazi Jewish heritage |
1 times greater |
The Canadian Breast Cancer Foundation encourages you to learn more about your breast health, breast cancer risk factors, and ways to reduce your risk. To inform your decisions, we also encourage you to consider speaking with a health care provider.
More Information
Sources
Canadian Breast Cancer Foundation – Ontario Region. (2010). Earlier Detection and Diagnosis of Breast Cancer. Recommendations and Scientific Review from It’s About Time! A Consensus Conference. Table on selected risk factors for breast cancer, adapted from the Susan G. Komen website.
Canadian Cancer Society’s Steering Committee on Cancer Statistics. Canadian Cancer Statistics 2011, Toronto, ON: Canadian Cancer Society, 2011.