Risk of breast cancer
A risk factor is a characteristic or factor that increases the likelihood of developing a disease. If the risk factor is present, there is an increased chance that the disease will develop. It has been estimated that 23% of breast cancer cases in the UK are preventable. (1).
The three main risk factors for developing breast cancer are being female, getting older and significant family history of breast cancer.
The main risk factor for cancer is older age. The estimated lifetime risk of getting breast cancer is 15% for females born after 1960 in the UK (2). The majority of women (80%) who get breast cancer are over the age of 50. The majority of men who get breast cancer are over 60. Though the risk of breast cancer increases with age, breast cancer tends to be more aggressive in younger people.
Men have a much lower risk of developing breast cancer than females. Male breast cancer patients tend to be older than female ones and the overall prognosis is worse for male than for female patients.
Of those diagnosed with breast cancer 5% have inherited a faulty breast cancer gene which increases risk of getting breast cancer. The two autosomal dominant genes, BRCA1 and BRCA2, account for the majority of cases of heredity breast cancer.
A small proportion of people have a higher change of getting breast cancer if there is a significant family history. This includes family who have had breast and ovarian cancer, family diagnosed with breast cancer at a young age and male relatives with breast cancer.
Other breast cancer risk factors
Persistently raised blood levels of the female hormone estrogen is associated with an increased risk of breast cancer. Circumstances where this occurs includes when women’s periods start before the age of 12, late menopause, delaying first childbirth and not breastfeeding.
Obesity increases the risk of developing breast cancer after the menopause.
History of breast cancer
Women who have already had breast cancer are at an increased risk of getting breast cancer in the same or opposite breast.
Having dense breast tissue
Breasts are described as being dense if they have less fatty tissue and more glandular and fibrous tissue. Women with dense breasts have a higher risk of developing breast cancer.
Certain benign breast conditions
There are many different benign breast diseases and most do not increase the risk of developing breast cancer, however there are some that may increase the risk.
People who have previously been diagnosed with breast, ovarian, uterine, or bowel cancer have a higher risk of developing breast cancer in the future.
Lifestyle risk factors
Hormone replacement therapy (HRT)
Studies have shown that taking HRT for a longer period of time increases the risk of developing breast cancer. The risk of developing breast cancer starts to reduce once it is stopped.
Hormonal contraceptives slightly increase the risk of breast cancer however this risk appears to be a short-term effect and reduces after stopping. After 10 years of stopping the risk is nearly the same compared to when not taking it.
Drinking any amount of alcohol increases the risk of developing breast cancer. The more you drink the greater the risk is.
There is some evidence that smoking may increase the risk of developing breast cancer. The risk appears to be greater for women who started smoking at a young age and continue to smoke for many years.
Oophorectomy and mastectomy
Prophylactic oophorectomy (removal of ovaries) and mastectomy in individuals with high-risk mutations of BRCA1 or BRCA2 genes reduces the risk of developing breast cancer as well as reducing the risk of developing ovarian cancer. Because of a complex balance of benefits and risks of a prophylactic surgery it is recommended only in very specific cases.
Brown KF, Rumgay H, Dunlop C, et al. The fraction of cancer attributable to known risk factors in England, Wales, Scotland, Northern Ireland, and the UK overall in 2015. British Journal of Cancer.
Lifetime risk estimates calculated by the Statistical Information Team at Cancer Research UK. Based on Office for National Statistics (ONS) 2016-based Life expectancies and population projections. Accessed December 2017, and Smittenaar CR,