Being a woman and getting older are the greatest risk factors – neither of which we can do much about! Breast cancer is relatively uncommon before the age of 30, but risk increases with age as a woman approaches and goes through menopause. Risk continues to rise with age following the menopause, but the rate of increase is less pronounced; 23% of women diagnosed are under 50, 41% aged 50 to 64, 36% over 65 (NCRI, 2009-2013). The chance of a woman in Ireland developing breast cancer by the age 79 is 1 in 10.
5 to 10% of breast cancer is hereditary and caused by inherited mutations (changes) in genes. Having one or more close relatives (sister, mother, daughter) who have been diagnosed with breast or ovarian cancer also increases a woman's risk of getting the disease
- particularly if more than one relative is affected
- the affected relative(s) were diagnosed under 40
Your father’s side of the family is as significant as your mother’s.
Certain groups such as women of Ashkenazi Jewish heritage have a much higher rate of these genes, as do Icelandic women
Female sex hormones
Many of the important risk factors for breast cancer relate to the female sex hormones (oestrogen and progesterone) and your lifetime exposure to these and other hormones:
- early onset of periods
- late age at first pregnancy
- late menopause
- few or no children
Being taller and a heavier weight at birth also seem to be significant risk factors.
But breastfeeding and having children early appear to reduce risk.
These relationships suggest that exposure to oestrogen plays a very significant role in breast cancer risk, and this is supported by the observations that current or recent use of oral contraceptives and hormone replacement therapy (HRT) also increase risk.
Aspects of lifestyle that appear to affect the risk of developing breast cancer include:
- Being overweight or obese (post-menopausal women)
- Drinking alcohol
- Physical inactivity
Even if you can’t prevent breast cancer you will improve your chances significantly if you are diagnosed early, so be sure to watch out for breast changes, report any to your doctor and attend screening if you are in the screening age group.While many risk factors are not modifiable, there are ways in which risk can be decreased:
- Maintain a healthy weight
- Exercise daily
- Eat a well-balanced diet
- Avoid or limit alcohol intake
Cancer in Ireland 1994-2016, with estimates for 2016-2018: Annual Report of the National Cancer Registry. National Cancer Registry, Cork, Ireland. (2018) www.ncri.ie
Breast Cancer Now (formerly Breakthrough Breast Cancer, Breast Cancer Campaign and Breast Cancer Care) www.breastcancernow.org [This website has very good information listing established, possible, and doubtful risk factors and has downloadable information.]
World Cancer Research Fund/American Institute for Cancer Research. Continuous Update Project 2018. Diet, nutrition, physical activity and breast cancer. Continuous Update Project Expert Report 2018. Available at dietandcancerreport.org .