1. Demographics and Risk Factors

​​Author: Dr. Nathalie Levasseur 
Date of completion: April 2026 
Date of next review: May 2027 ​​

See Breast Clinical Care Pathway

Breast Cancer is a leading cancer in women in all countries. Anticipated average lifetime risk is 1 in 8.1,2 

​A summary of known risk factors for breast cancer is shown in Table 1 below, which also indicates the strength of the risk factor in the development of breast cancer.3 

 

Table 1: Risk Factors Associated with Breast Cancer  

Modifiable Risk Factors 

  • Obesity  
  • Physical Activity ​
  • Alcohol consumption 
  • Diet 
  • Smoking 
  • Hormone replacement therapy (long term usage, systemically absorbed) 

 

Non-Modifiable Risk Factors 

  • Personal history of breast cancer 
  • Family history of breast cancer (including males) 
  • Genetic mutations (Hereditary Cancer & High Risk Clinic) 
  • Female sex at birth 
  • Older age 
  • Nulliparity 
  • Older age at first birth (over age 30) 
  • Early menstruation & delayed menopause  
  • Socioeconomic status 
  • Race/ethnicity 
  • Prior breast abnormality requiring biopsy  
  • ​Increased breast density 
  • Prior chest wall radiotherapy treatment 
  • Breastfeeding (potentially protective) *evidence conflicting* 

 

References 

    1. ​​Public Health Agency of Canada. Breast cancer. https://www.canada.ca/en/public-health/services/chronic-diseases/cancer/breast-cancer.html. Accessed 2026 Apr 29. 

    2. Canadian Cancer Society. Breast cancer statistics. https://cancer.ca/en/cancer-information/cancer-types/breast/statistics. Accessed 2026 Apr 29. 

    3. Łukasiewicz S, Czeczelewski M, Forma A, Baj J, Sitarz R, Stanisławek A. Breast Cancer-Epidemiology, Risk Factors, Classification, Prognostic Markers, and Current Treatment Strategies-An Updated Review. Cancers (Basel). 2021 Aug 25;13(17):4287. doi: 10.3390/cancers13174287. PMID: 34503097; PMCID: PMC8428369 ​