Breast cancer are known as high penetrance genes. A breast cancer gene's penetrance is the likelihood that someone with a mutated gene will develop breast cancer during their lifetime. A person with a high penetrance breast cancer gene has a high risk of breast cancer and a strong family history of breast cancer because high penetrance genes are thought to largely act alone, diseases associated with them are sometimes called single gene disorders. But the effects of these genes can be modified by other genes as well as by the environment inside and outside the body.
Inherited breast cancer risk seen in families with only a few cases of breast cancer results from a second type of mutated genes, low penetrance genes. Low penetrance genes are much more common than high penetrance genes.
The breast cancer risk of women who carry these genes depends largely on the interactions of the low penetrance genes with other genes and with the body's internal and external environments. Since low penetrance genes are much more common than the high penetrance genes, low penetrance genes account for more cases of breast cancer overall. If inherited mutations are only responsible for about one quarter of all breast cancer risk (27%), what is the source of the rest of the risk?
Three quarters of cases of breast cancer are not due to inheritance. Instead, they are the result of biological and environmental factors to which women are exposed. These factors can include:
1. Reproductive hormone levels and how long women are exposed to them (for example, age of menarche and menopause).
2. Women's child-bearing patterns (for example, at what age they bear children, how long they breast feed and how many children they have).
3. Medical treatments associated with breast cancer risk (for example, oral contraceptives, or postmenopausal hormone treatment).
4. Women's physical characteristics (for example, body weight and where fat is carried on the body); exposure to toxic chemicals associated with breast cancer risk.
5. Exposure to radiation, especially at young ages, and parts of the diet associated with breast cancer risk (for example, alcohol use).
These environmental and lifestyle factors may also act together with genetic factors.
Inherited breast cancer risk seen in families with only a few cases of breast cancer results from a second type of mutated genes, low penetrance genes. Low penetrance genes are much more common than high penetrance genes.
The breast cancer risk of women who carry these genes depends largely on the interactions of the low penetrance genes with other genes and with the body's internal and external environments. Since low penetrance genes are much more common than the high penetrance genes, low penetrance genes account for more cases of breast cancer overall. If inherited mutations are only responsible for about one quarter of all breast cancer risk (27%), what is the source of the rest of the risk?
Three quarters of cases of breast cancer are not due to inheritance. Instead, they are the result of biological and environmental factors to which women are exposed. These factors can include:
1. Reproductive hormone levels and how long women are exposed to them (for example, age of menarche and menopause).
2. Women's child-bearing patterns (for example, at what age they bear children, how long they breast feed and how many children they have).
3. Medical treatments associated with breast cancer risk (for example, oral contraceptives, or postmenopausal hormone treatment).
4. Women's physical characteristics (for example, body weight and where fat is carried on the body); exposure to toxic chemicals associated with breast cancer risk.
5. Exposure to radiation, especially at young ages, and parts of the diet associated with breast cancer risk (for example, alcohol use).
These environmental and lifestyle factors may also act together with genetic factors.
