Understanding your own level of risk allows you to be appropriately monitored for breast cancer.
Most women are not in a high-risk group and don’t ever develop breast cancer. However, understanding your own level of risk allows you to be properly monitored for breast cancer. Risk can be divided into three categories, and you might move into different categories throughout your life, or if your family history alters.
Sporadic Cancers (general population risk)
The vast majority of women fall into this category. These women will have around an 11% risk of developing breast cancer by the age of 85. These cancers occur by chance, or because of environmental factors.
It’s important to remember that most women who develop breast cancer will have no family history of the disease, and their cancer isn’t inherited, even if they do have a relative with breast cancer. Women in this group do not need to be referred for genetic testing.
Familial Cancers (moderate risk)
Women in this category may have genetic mutations which result in a moderately increased cancer risk, but if they develop breast cancer, it’s because of a combination of genetic and environmental causes. There may be more cases of a specific type of cancer within a family than statistically expected, but no specific pattern of inheritance.
Individuals in this group may have:
- One first-degree relative diagnosed with breast cancer before the age of 50
- Two first-degree relatives diagnosed with breast cancer after the age of 50
- Two second-degree relatives diagnosed with breast cancer before the age of 50
- Three first- or second-degree relatives diagnosed at any age
Hereditary Cancers (high risk)
If an individual has inherited a faulty copy of a protective gene, the function of the gene is altered, and they can be at higher risk of developing cancer. This faulty copy is referred to as a “mutation”. Genetic mutations which cause cancer are much rarer than mutations caused by ageing or other factors.
First-degree relatives (parents, siblings, and children) of an affected individual have a 50% chance of having the same mutation. Those who do not have the mutation have the same cancer risk as the general population. If a genetic mutation is inherited, there is a risk that cancers can develop at a younger age than usual, and could grow in multiple sites.
Potentially high-risk women may have one of the following in their family history:
- One first- or second-degree relative with breast or ovarian cancer and a male relative with breast cancer or Ashkenazi Jewish ancestry.
- Two first- or second-degree relatives diagnosed with breast cancer before an average age of 45 (at least one must be a first-degree relative).
- Three first-degree or second-degree relatives diagnosed with breast cancer before an average age of 60 (one must be a first-degree relative).
- Four relatives diagnosed with breast cancer at any age (one must be a first-degree relative).
- One first-degree relative with cancer in both breasts, where the first cancer was diagnosed before 50.
- One first-degree or one second-degree relative diagnosed with ovarian cancer at any age, and one first or second-degree relative diagnosed with breast cancer before 50.
- Two first- or second-degree relatives diagnosed with ovarian cancer at any age.
- One first- or second-degree relative with both breast and ovarian cancer.
Note: First-degree relatives are parents, siblings (sisters or brothers) and children.
Second-degree relatives are grandparents, aunts and uncles, nephews and nieces, grandchildren, and half-siblings.
First cousins, great–grandparents, great aunts and uncles, great nieces and nephews and great-grandchildren are third-degree relatives.
Are you at moderate or high risk of breast cancer?
If you believe you are at moderate or high risk of breast cancer, talk to your GP about it. They can let you know if you should be having extra screening, or refer you for genetic assessment.