Breast Health: Breast Cancer Risk Factors
Breast Cancer Risk Factors
Every woman wants to know what she can do to lower her risk of breast cancer. Some of the factors associated with breast cancer -- being a woman, your age, and your genetics, for example -- can't be changed. Other factors -- maintaining a healthy weight, exercising, smoking cigarettes, and eating nutritious food -- can be changed by making choices. By choosing the healthiest lifestyle options possible, you can empower yourself and make sure your breast cancer risk is as low as possible.
The known risk factors for breast cancer are listed below. Click on each link to learn more about the risk factor and ways you can minimize it in your own life. If a factor can't be changed (such as your genetics), you can learn about protective steps you can take that can help keep your risk as low as possible.
Established risks:
Just being a woman is the biggest risk factor for developing breast cancer. There are about 190,000 new cases of invasive breast cancer and 60,000 cases of non-invasive breast cancer this year in American women. While men do develop breast cancer, less than 1% of all new breast cancer cases happen in men. Approximately 2,000 cases of breast cancer will be diagnosed in American men this year.
The biggest reasons for the difference in breast cancer rates between men and women are:
Women's breast development takes 3 to 4 years and is usually complete by age 14. It's uncommon for men's breasts to fully form -- most of the male breasts you see are fat, not formed glands.
Once fully formed, breast cells are very immature and highly active until a woman's first full-term pregnancy. While they are immature, a women's breast cells are very responsive to estrogen and other hormones, including hormone disrupters in the environment.
Men's breast cells are inactive and most men have extremely low levels of estrogen.
So hormonal stimulation of highly responsive and vulnerable breast cells in women, particularly during the extra-sensitive period of breast development, is why breast cancer is much more common in women than in men.
Age
Everyone alive is growing older. And as with many other diseases, your risk of breast cancer goes up as you get older. For example, according to the American Cancer Society, about 1 out of 8 invasive breast cancers develop in women younger than 45. About 2 out of 3 invasive breast cancers are found in women 55 or older.
In fact, the aging process is the biggest risk factor for breast cancer. That's because the longer we live, there are more opportunities for genetic damage (mutations) in the body. And as we age, our bodies are less capable of repairing genetic damag
In fact, the aging process is the biggest risk factor for breast cancer. That's because the longer we live, there are more opportunities for genetic damage (mutations) in the body. And as we age, our bodies are less capable of repairing genetic damag
Family History:
Women with close relatives who've been diagnosed with breast cancer have a higher risk of developing the disease.
If you've had one first-degree female relative (sister, mother, daughter) diagnosed with breast cancer, your risk is doubled. If two first-degree relatives have been diagnosed, your risk is 5 times higher than average.
If your brother or father have been diagnosed with breast cancer, your risk is higher, though researchers aren't sure how much higher.
In some cases, a strong family history of breast cancer is linked to having an abnormal gene associated with a high risk of breast cancer, such as the BRCA1 or BRCA2 gene. In other cases, an abnormal CHEK2 gene may play a role in developing breast cancer.
If you've had one first-degree female relative (sister, mother, daughter) diagnosed with breast cancer, your risk is doubled. If two first-degree relatives have been diagnosed, your risk is 5 times higher than average.
If your brother or father have been diagnosed with breast cancer, your risk is higher, though researchers aren't sure how much higher.
In some cases, a strong family history of breast cancer is linked to having an abnormal gene associated with a high risk of breast cancer, such as the BRCA1 or BRCA2 gene. In other cases, an abnormal CHEK2 gene may play a role in developing breast cancer.
Genetics
About 5% to 10% of breast cancers are thought to be hereditary, caused by abnormal genes passed from parent to child.
Genes are particles in cells, contained in chromosomes, and made of DNA (deoxyribonucleic acid). DNA contains the instructions for building proteins. And proteins control the structure and function of all the cells that make up your body.
Think of your genes as an instruction manual for cell growth and function. Abnormalities in the DNA are like typographical errors. They may provide the wrong set of instructions, leading to faulty cell growth or function. In any one person, if there is an error in a gene, that same mistake will appear in all the cells that contain the same gene. This is like having an instruction manual in which all the copies have the same typographical error.
BRCA1 and BRCA2 genes
Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two).
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and breast cancer risk increases. Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers, or 1 out of every 10 cases.
Having an abnormal BRCA1 or BRCA2 gene doesn't mean you will be diagnosed with breast cancer. Researchers are learning that other mutations in pieces of chromosomes -- called SNPs (single nucleotide polymorphisms) -- may be linked to higher breast cancer risk in women with an abnormal BRCA1 gene as well as women who didn't inherit an abnormal breast cancer gene.
Women who are diagnosed with breast cancer and have an abnormal BRCA1 or BRCA2 gene often have a family history of breast cancer, ovarian cancer, and other cancers. Still, most people who develop breast cancer did not inherit an abnormal breast cancer gene and have no family history of the disease.
You are substantially more likely to have an abnormal breast cancer gene if:
You have blood relatives (grandmothers, mother, sisters, aunts) on either your mother's or father's side of the family who had breast cancer diagnosed before age 50.
There is both breast and ovarian cancer in your family, particularly in a single individual.
There are other gland-related cancers in your family such as pancreatic, colon, and thyroid cancers.
Women in your family have had cancer in both breasts.
You are of Ashkenazi Jewish (Eastern European) heritage.
You are African American and have been diagnosed with breast cancer at age 35 or younger.
A man in your family has had breast cancer.
If one family member has an abnormal breast cancer gene, it does not mean that all family members will have it.
The average woman in the United States has about a 1 in 8, or a 12-13%, risk of developing breast cancer in her lifetime. Women who have an abnormal BRCA1 or BRCA2 gene (or both) can have up to an 80% risk of being diagnosed with breast cancer during their lifetimes. Breast cancers associated with an abnormal BRCA1 or BRCA2 gene tend to develop in younger women and occur more often in both breasts than cancers in women without these abnormal genes.
Women with an abnormal BRCA1 or BRCA2 gene also have an increased risk of developing ovarian, colon, pancreatic, and thyroid cancers, as well as melanoma.
Men who have an abnormal BRCA2 gene have a higher risk for breast cancer than men who don't -- about 8% by the time they're 80 years old. This is about 80 times greater than average.
Men with an abnormal BRCA1 gene have a slightly higher risk of prostate cancer. Men with an abnormal BRCA2 gene are 7 times more likely than men without the abnormal gene to develop prostate cancer. Other cancer risks, such as cancer of the skin or digestive tract, also may be slightly higher in men with abnormal BRCA1 or BRCA2 genes.
Other genes
Changes in other genes are also associated with breast cancer. These abnormal genes are much less common and don't seem to increase risk as much as abnormal BRCA1 and BRCA2 genes, which are considered rare. Still, because these genetic mutations are rarer, they haven't been studied as much as the BRCA genes.
ATM: The ATM gene helps repair damaged DNA. DNA carries genetic information in cells. Inheriting two abnormal copies of this gene causes the disease ataxia-telangiectasia, a rare disease that affects brain development. Inheriting one abnormal ATM gene has been linked to an increased rate of breast cancer in some families because the abnormal gene stops the cells from repairing damaged DNA.
p53 (also called the TP53 gene): The p53 gene provides instructions to the body for making a protein that stops tumor growth. Inheriting an abnormal p53 gene causes Li-Fraumeni syndrome, a disorder that causes people to develop soft tissue cancers at a young age. People with this rare syndrome have a higher-than-average-risk of breast cancer and several other cancers, including leukemia, brain tumors, and sarcomas (cancer of the bones or connective tissue).
CHEK2: The CHEK2 gene also provides instructions for making a protein that stops tumor growth. Li-Fraumeni syndrome also can be caused by an inherited abnormal CHEK2 gene. Even when an abnormal CHEK2 gene doesn't cause Li-Fraumeni syndrome, it can double breast cancer risk.
PTEN: The PTEN gene helps regulate cell growth. An abnormal PTEN gene causes Cowden syndrome, a rare disorder in which people have a higher risk of both benign (not cancer) and cancerous breast tumors, as well as growths in the digestive tract, thyroid, uterus, and ovaries.
CDH1: The CDH1 gene makes a protein that helps cells bind together to form tissue. An abnormal CDH1 gene causes a rare type of stomach cancer at an early age. Women with an abnormal CDH1 gene also have an increased risk of invasive lobular breast cancer.
Genetic testing
There are genetic tests available to determine if someone has an abnormal BRCA1 or BRCA2 gene. A genetic counselor also may order testing for an abnormal ATM, p53, CHEK2, PTEN, or CDH1 gene if it's determined from your personal or family history that these tests are needed.
For more information, visit the Breastcancer.org Genetic Testing pages.
Genes are particles in cells, contained in chromosomes, and made of DNA (deoxyribonucleic acid). DNA contains the instructions for building proteins. And proteins control the structure and function of all the cells that make up your body.
Think of your genes as an instruction manual for cell growth and function. Abnormalities in the DNA are like typographical errors. They may provide the wrong set of instructions, leading to faulty cell growth or function. In any one person, if there is an error in a gene, that same mistake will appear in all the cells that contain the same gene. This is like having an instruction manual in which all the copies have the same typographical error.
BRCA1 and BRCA2 genes
Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two).
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and breast cancer risk increases. Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers, or 1 out of every 10 cases.
Having an abnormal BRCA1 or BRCA2 gene doesn't mean you will be diagnosed with breast cancer. Researchers are learning that other mutations in pieces of chromosomes -- called SNPs (single nucleotide polymorphisms) -- may be linked to higher breast cancer risk in women with an abnormal BRCA1 gene as well as women who didn't inherit an abnormal breast cancer gene.
Women who are diagnosed with breast cancer and have an abnormal BRCA1 or BRCA2 gene often have a family history of breast cancer, ovarian cancer, and other cancers. Still, most people who develop breast cancer did not inherit an abnormal breast cancer gene and have no family history of the disease.
You are substantially more likely to have an abnormal breast cancer gene if:
You have blood relatives (grandmothers, mother, sisters, aunts) on either your mother's or father's side of the family who had breast cancer diagnosed before age 50.
There is both breast and ovarian cancer in your family, particularly in a single individual.
There are other gland-related cancers in your family such as pancreatic, colon, and thyroid cancers.
Women in your family have had cancer in both breasts.
You are of Ashkenazi Jewish (Eastern European) heritage.
You are African American and have been diagnosed with breast cancer at age 35 or younger.
A man in your family has had breast cancer.
If one family member has an abnormal breast cancer gene, it does not mean that all family members will have it.
The average woman in the United States has about a 1 in 8, or a 12-13%, risk of developing breast cancer in her lifetime. Women who have an abnormal BRCA1 or BRCA2 gene (or both) can have up to an 80% risk of being diagnosed with breast cancer during their lifetimes. Breast cancers associated with an abnormal BRCA1 or BRCA2 gene tend to develop in younger women and occur more often in both breasts than cancers in women without these abnormal genes.
Women with an abnormal BRCA1 or BRCA2 gene also have an increased risk of developing ovarian, colon, pancreatic, and thyroid cancers, as well as melanoma.
Men who have an abnormal BRCA2 gene have a higher risk for breast cancer than men who don't -- about 8% by the time they're 80 years old. This is about 80 times greater than average.
Men with an abnormal BRCA1 gene have a slightly higher risk of prostate cancer. Men with an abnormal BRCA2 gene are 7 times more likely than men without the abnormal gene to develop prostate cancer. Other cancer risks, such as cancer of the skin or digestive tract, also may be slightly higher in men with abnormal BRCA1 or BRCA2 genes.
Other genes
Changes in other genes are also associated with breast cancer. These abnormal genes are much less common and don't seem to increase risk as much as abnormal BRCA1 and BRCA2 genes, which are considered rare. Still, because these genetic mutations are rarer, they haven't been studied as much as the BRCA genes.
ATM: The ATM gene helps repair damaged DNA. DNA carries genetic information in cells. Inheriting two abnormal copies of this gene causes the disease ataxia-telangiectasia, a rare disease that affects brain development. Inheriting one abnormal ATM gene has been linked to an increased rate of breast cancer in some families because the abnormal gene stops the cells from repairing damaged DNA.
p53 (also called the TP53 gene): The p53 gene provides instructions to the body for making a protein that stops tumor growth. Inheriting an abnormal p53 gene causes Li-Fraumeni syndrome, a disorder that causes people to develop soft tissue cancers at a young age. People with this rare syndrome have a higher-than-average-risk of breast cancer and several other cancers, including leukemia, brain tumors, and sarcomas (cancer of the bones or connective tissue).
CHEK2: The CHEK2 gene also provides instructions for making a protein that stops tumor growth. Li-Fraumeni syndrome also can be caused by an inherited abnormal CHEK2 gene. Even when an abnormal CHEK2 gene doesn't cause Li-Fraumeni syndrome, it can double breast cancer risk.
PTEN: The PTEN gene helps regulate cell growth. An abnormal PTEN gene causes Cowden syndrome, a rare disorder in which people have a higher risk of both benign (not cancer) and cancerous breast tumors, as well as growths in the digestive tract, thyroid, uterus, and ovaries.
CDH1: The CDH1 gene makes a protein that helps cells bind together to form tissue. An abnormal CDH1 gene causes a rare type of stomach cancer at an early age. Women with an abnormal CDH1 gene also have an increased risk of invasive lobular breast cancer.
Genetic testing
There are genetic tests available to determine if someone has an abnormal BRCA1 or BRCA2 gene. A genetic counselor also may order testing for an abnormal ATM, p53, CHEK2, PTEN, or CDH1 gene if it's determined from your personal or family history that these tests are needed.
For more information, visit the Breastcancer.org Genetic Testing pages.
Personal History of Breast Cancer
If you've been diagnosed with breast cancer, you're 3 to 4 times more likely to develop a new cancer in the other breast or a different part of the same breast. This risk is different from the risk of the original cancer coming back (called risk of recurrence).
If you've been diagnosed with breast cancer, you're 3 to 4 times more likely to develop a new cancer in the other breast or a different part of the same breast. This risk is different from the risk of the original cancer coming back (called risk of recurrence).
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