To date, we still do not know exactly what triggers breast cancer, but certain factors have been identified that are associated with an increased risk of developing the disease.
Age. This is the main risk factor linked to the onset of breast cancer. Risk increases with age.
The hormonal cycles a woman experiences during her lifetime. Breast cancer development is affected by the action of hormones (oestrogens) on breast tissue. The early appearance of the first menstruation, a late menopause or the post-menopause use of hormone replacement therapy all increase the risk of breast cancer. Women who have never given birth (nulliparous) are also associated with a greater risk.
Family history. Individuals with a family history of breast cancer have a greater risk. This risk is greater when they are first-degree relatives (mother, sister or daughter).
Women who have previously had breast cancer or a benign proliferative breast disease have an increased risk of developing breast cancer in the future.
High breast density is associated with a greater risk of breast cancer.
Exposure to ionising radiation, especially during puberty, and inherited mutations related to breast cancer both increase the risk.
Alcohol consumption and obesity also escalate the risk of developing breast cancer.
BRCA1 and BRCA2 mutations
The genes BRCA1 and BRCA2 (BReast CAncer susceptibility gene 1 and 2) produce tumour-suppressor proteins that help repair damaged DNA, regulate cell cycle and prevent uncontrolled proliferation. If one of these genes has a mutation or becomes altered, for example if it no longer produces its protein or the protein does not work correctly, then it is unable to repair damaged DNA correctly.
Specific inherited mutations in BRCA1 and BRCA2 increase the risk of breast and ovarian cancers; they are also associated with a greater risk of other types of cancer. BRCA1 and BRCA2 mutations collectively represent 5–10% of all breast cancers.
A blood analysis and genetic study are required to determine whether or not an individual carries one of these mutations.