How common is breast cancer?

Worldwide, breast cancer is the most common form of cancer in women. In 2016, it is estimated that 25,700 Canadian women developed breast cancer. Men can also develop breast cancer, although it is rare (only one in every 100 breast cancer cases).

What is my chance of developing breast cancer?

The chance of developing breast cancer increases with age. For the average North American woman, the chance of developing breast cancer would be:

  • By age 25  – less than 1 in 1,000
  • By age 50 – 1 in 63
  • By age 75 – 1 in 15
  • By age 90 – 1 in 9

What are the risk factors for breast cancer?

We don’t know what causes breast cancer. However, there are certain risk factors that can increase the chance of developing breast cancer.

Risk factors that you cannot change:

  • Being female
  • Growing older: the risk of breast cancer increases throughout a woman’s life. Breast cancer is rare before age 30 but is much more common after age 50
  • BRCA1 or BRCA2 gene mutation: some people inherit an abnormality (a mutation) in one of these genes, whose function is to repair cell damage and keep breast cells growing normally
  • A strong family history of breast cancer: certain patterns of breast cancer in the family increase the risk of hereditary breast cancer
  • A personal history of breast cancer (if you’ve had breast cancer in one breast, your risk is increased of developing cancer in your other breast)
  • Dense breasts (as seen on a mammogram)
  • Beginning your period at early age, generally before age 12
  • Beginning menopause at an older age (55+)
  • Previous chest radiation. Some young women have had radiation to the chest to treat Hodgkin’s or non-Hodgkin’s lymphoma
  • Hyperplasia: hyperplasia and atypical hyperplasia are conditions in which an overgrowth of cells is found in the breast lobules or ducts.  With atypical hyperplasia, the cells are also abnormal
  • Lobular carcinoma in situ (LCIS): this is a condition in which abnormal cells are found in the breast lobules but have not spread to the nearby tissue. There are more abnormal cells in the lobule with LCIS than with atypical hyperplasia

Risk factors that you may have some control over:

  • Never breastfeeding
  • An unhealthy body weight
  • Drinking alcohol in excess
  • Being inactive
  • Tobacco use
  • Having your first full-term pregnancy after the age of 30
  • Never giving birth to a full-term baby
  • Postmenopausal hormone therapy

Many women will have some of these risk factors. Having one or more risk factors does not mean you will be diagnosed with breast cancer. Also, many women who get breast cancer do not have any known risk factors, other than simply being a woman and aging.

I’ve heard that using antiperspirants and underwire bras can cause breast cancer – is this true?

There are many myths around what does and does not increase the risk of breast cancer. Research has shown that the following factors do not increase your risk:

  • Antiperspirants AND deodorants
  • Abortions
  • Bras, including underwire bras
  • Bruising, squeezing or other injury to the breast
  • Hair dye

How can I reduce my risk of getting breast cancer?

Although you can’t control some of the factors that may increase the risk of breast cancer, there are steps you can take to protect yourself in other ways. A healthy lifestyle may reduce the risk of many types of cancer, including breast cancer, as well as heart disease, stroke and osteoporosis. A healthy lifestyle includes:

  • Eating a well-balanced diet, with plenty of vegetables and fruit and foods low in animal fat
  • Limiting alcohol to not more than one drink a day, on average
  • Exercising regularly
  • Staying at a healthy weight
  • Not smoking
  • Following cancer-screening guidelines to help detect cancer early
  • Seeing your doctor for regular check-ups

Links to more information

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Preventative Health and Breast Cancer Risk Reduction
Canadian Breast Cancer Foundation

Breast Cancer and Your Risk
Public Health Agency of Canada

Reduce Your Risk of Breast Cancer
Canadian Cancer Society