Breast Cancer

Breast cancer is the most common cancer in Canadian women, with the exception of non-melanoma skin cancer. While it can also be found in men, male breast cancer is a very rare occurrence. Breast cancer starts in the cells of the mammary gland. Breast tissue covers a larger area than just the breast, extending up to the collarbone and from the armpit to the breastbone.

  • In 2017 an estimated 26,300 Canadian women will be diagnosed with breast cancer and 5,000 will die of it.
  • Breast cancer accounts for approximately 26% on new cases of cancer and 13% of all cancer deaths in Canadian women.
  • 1 in 8 women are expected to develop breast cancer during her lifetime and 1 in 31 will die of it.
  • In 2009, an estimated 157,360 women were living with, or surviving from, breast cancer in Canada. That means that 1 in 107 Canadian women were diagnosed with breast cancer at some point during the 10 years prior to 2009.
  • Almost all breast cancers start in the glandular tissue of the breast and are known as adenocarcinomas. Cancer cells may start within the ducts (ductal carcinoma) or lobules (lobular carcinoma). Ductal carcinoma is the most common type of breast cancer, accounting for approximately 90% of all in situ breast carcinomas and 70% of all invasive breast carcinomas.
  • What should I know about breast cancer?

Please refer to the Breast Cancer in Canada infographic for more information

Risk Factors

There is no single cause of breast cancer but some factors that increase the risk of developing the disease include:

  • Age: 82% of the cases of breast cancer occur in women over 50 years of age.
  • Family history of breast cancer, especially in a mother, sister or daughter diagnosed before menopause, or if a mutation on the BRCA1 or BRCA2 genes is present.
  • Previous breast disorders with biopsies showing abnormal cells.
  • No full term pregnancies or having a full term first pregnancy after age 30.
  • In post-menopausal women: obesity and physical inactivity.
  • Beginning to menstruate at an early age.
  • Later than average menopause.
  • Taking hormone replacement therapy (estrogen plus progestin) for more than 5 years.
  • The effects of smoking and never breastfeeding are currently under study.
  • What can I do to reduce my risk of cancer?
  • How should I eat to reduce my risk of cancer?

Managing Breast Cancer

Facts & Figures

Knowledge Development and Exchange

Agency-funded initiatives

The Public Health Agency of Canada recently funded two projects aimed at raising awareness and preventing breast cancer:

  • The "Breast Health Program", led by the Canadian Breast Cancer Foundation - Ontario Region, aimed to increase awareness and understanding among Ontario women aged 40+ of the behaviours required to reduce the risk of breast cancer; and,
  • The High Risk Breast Cancer Project, which aimed to increase awareness and understanding among women, health care providers and the general public about the factors that place women at high risk for developing breast cancer, including hereditary breast cancer. This was a collaborative effort between various breast cancer organizations, including: Canadian Breast Cancer Foundation, Canadian Breast Cancer Network, Rethink Breast Cancer, and Willow Breast Cancer Support Canada.
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