Risk Factors

A risk factor is something that can increase the chance that breast cancer will occur. There are several risk factors for breast cancer. Many risk factors for breast cancer cannot be changed or controlled. Some risk factors are stronger than others. The strongest risk factors for breast cancer are your age, having a genetic mutation or a family history of breast cancer, breast density, atypical breast hyperplasia, lobular carcinoma in situ (LCIS), or radiation treatment as a child.

Learn more about the risk factors for breast cancer that you can control and those that you cannot control.

Factors You Can Control

Factors You Cannot Control

Learn how you can be more proactive. Prevent and detect breast cancer early.

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Alcohol Use

Do you consume two or more alcoholic beverages per day?

If the answer is yes:

  • Generally, the greater the number of alcoholic beverages consumed the greater the risk. Women who drink two or more beverages per day are at increased risk for breast cancer. Four drinks per day can increase your risk by 40 percent compared to women who do not drink at all. Decrease your alcoholic beverage consumption to fewer than two alcoholic beverages per day to lower your risk.
  • Some alcohol (but fewer than two drinks per day) may be good for your heart and blood vessels.

If the answer is no:

  • Drinking fewer than two alcoholic beverages per day is not thought to be associated with an increased breast cancer risk.
  • Some alcohol (but fewer than two drinks per day) may be good for your heart and blood vessels.

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Breastfeeding

Have you breastfed for a total of at least one year?

If the answer is yes:

  • Studies show that breastfeeding slightly decreases breast cancer risk. Reasons for this are unclear, but it may be because breastfeeding reduces the number of menstrual cycles.
  • Breastfeeding for longer than one year and at younger ages appears to reduce the risk further.

If the answer is no:

  • If you are undecided about whether you would like to breastfeed your children, consider that studies have shown that breastfeeding for at least one year slightly decreases the risk for breast cancer.
  • Breastfeeding for longer and at younger ages appears to reduce the risk further.

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Having Children

Did you give birth to children before you turned 30?

If the answer is yes:

  • Generally, the younger you are when give birth to your first child, the lower your lifetime risk to develop breast cancer. Women who complete their first pregnancy before the age of 30 are a little less likely to develop breast cancer throughout their lifetime than those who wait until after 30. This may be because childbearing causes the cells in the breast to replicate and divide rapidly. As people age, their DNA become more damaged. Therefore, the breasts of older women are more likely to have damaged DNA that can cause cancer when replicated more rapidly.
  • Having children at any age is associated with a decrease breast cancer risk. There is a slightly further decrease in lifetime risk for breast cancer after each additional childbirth.

If the answer is no:

  • Women who give birth to their first child after the age of 30 are slightly more likely to develop breast cancer than women who have completed a pregnancy earlier in their lives. This may be because childbearing causes the cells in the breast to replicate and divide rapidly. As people age, their DNA become more damaged. Therefore, the breasts of older women are more likely to have damaged DNA that can cause cancer when replicated more rapidly.
  • Regardless of age, women who complete a pregnancy at any point in their lives are less likely to develop cancer than women who do not.

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Hormonal Replacement Therapy (HRT)

Have you used combined hormonal therapy (estrogen+progestin) within the past 5-10 years? For example: Activella, Femhrt, Prempro, Ortho-Prefest, or Premphase

  • Post-menopausal hormonal therapy that contains progestin and estrogen is associated with an elevated breast cancer risk. The risk for breast cancer doubles after five years of use. There is also an increased risk for ovarian cancer, heart disease, stroke, and blood clots in the lungs. Speak with your doctor if you would like to stop using combined hormonal therapy.
  • However, you may have helped to reduce your risk of colon cancer and osteoporosis. 

Have you used estrogen-only hormonal therapy? For example: Cenestin, Enjuvia, or Premarin

It is unclear whether estrogen-only HRT is associated with breast cancer risk. Individuals who may be at increased risk for breast cancer when taking estrogen-only HRT include women who:

  • Have used estrogen-only HRT for 10 or more years.
  • Have other risk factors, including family history of breast cancer and specific benign breast diseases.

A few studies have shown that estrogen-only HRT may slightly reduce the risk of breast cancer for other women. Estrogen-only HRT is associated with an increased risk for strokes and ovarian cancer. However, it may also lower the risk for colon cancer and osteoporosis. Estrogen-only HRT is only an option for women who have had their uterus removed.

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Oral Contraception/Birth Control Pills

Do you use oral contraception? Examples: Loestrin, Microgestin, Ortho Tri-Cyclen, Yasmin, or Yaz

  • Older studies had shown that women on birth control pills were a little more likely to develop breast cancer. However, some evidence shows that today’s lower-dose pills are not associated with an increased risk for breast cancer.
  • Research suggests that women who have not used oral contraception within the past 10 years are not at increased risk for breast cancer. You should talk with your doctor if you are considering stopping use.
  • Oral contraception can increase the chance for heart attack and stroke in women who have other risk factors for these health problems, including heavy smokers.
  • If taken for five or more years, birth control pills can reduce the risk of ovarian, uterine, and colon cancer.

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Physical Activity

Do you exercise regularly?

If the answer is yes:

  • Great! Some research shows that 30 minutes of engagement in physical activity every day, or 45 to 60 minutes of intentional physical activity five or more days per week, can reduce your risk for breast cancer. New research suggests that this activity can be broken down into smaller increments and spread throughout the day.
  • Research shows that breast cancer survivors who engage in regular physical activity reduce their risk of recurrence and decrease premature mortality. Studies suggest this may be because exercise lowers insulin levels. High levels of insulin have been associated with an increased breast cancer risk.
  • You have also helped to lower your risk for other types of cancers, in addition to stroke, diabetes, and heart disease.

If the answer is no:

  • Although the association between physical activity and breast cancer risk has not been strongly established, research suggests that engaging in regular physical activity may reduce your risk.
  • You do not need to engage in strenuous exercise to benefit; even brisk walking can help. Aim for at least 30 minutes every day, or 45 to 60 minutes of intentional physical activity five or more days per week. Physical activity also will help to reduce your risk for other cancers, stroke, diabetes, and heart disease. 
  • It is not too late! If you are a breast cancer survivor, you can reduce your risk of recurrence by starting a physical activity routine. Even brisk walking for a few hours each week can make a significant impact on your breast cancer risk. Try breaking up your exercise routine into several smaller sessions throughout your day.

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Weight

Are you considered by health care providers to be overweight or obese?

If the answer is yes:

  • Being overweight is associated with an increased risk for breast cancer. This association is especially true in post-menopausal women. This may be because stored fat is a source of estrogen. In women who have gone through menopause, fat is likely their primary source of estrogen. Also, women who are overweight tend to have higher blood insulin levels, which have been associated with an increased risk for multiple cancers.
  • Consider speaking with your health care providers about finding healthy ways to lower your weight.

If the answer is no:

  • Keeping a lower, healthy weight can slightly reduce your risk of breast cancer. This association may be especially true in post-menopausal women. This may be because stored fat is a source of estrogen. In women who have gone through menopause, fat is likely their primary source of estrogen. Also, women who are overweight tend to have higher blood insulin levels, which have been associated with an increased risk for multiple cancers.
  • Consider maintaining your weight, and avoid gaining weight, even in early adulthood. Women who gain significant weight may be more likely to develop breast cancer.

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Factors You Cannot Control

Age

Everyone’s risk to develop cancer increases with age. Cancer usually takes years to develop. About two out of three breast cancers occur in women over the age of 55, and the average age of diagnosis is 61 for women and 68 for men. Only 5 percent of women with breast cancer are diagnosed under the age of 40.  

            Age                  Risk for breast cancer

            30                    1 in 2,212

            40                    1 in 235

            50                    1 in 54

            60                    1 in 23

            70                    1 in 14

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Dense Breasts

  • Women with dense breasts appear to have an elevated risk for breast cancer. Breast density is measured, somewhat subjectively, by mammogram.
  • It is harder to detect breast cancer in women who have dense breasts.

Diethylstilbestrol (DES) Use

  • DES was used by pregnant women in the 1970s to lower the risk of miscarriage. These women have a slightly higher risk to develop breast cancer.
  • Women whose mothers took DES while pregnant also may have an increased risk to develop breast cancer.

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Ethnicity

  • Women of Caucasian ancestry generally have a slightly higher risk to develop breast cancer.
  • Women of eastern European (Ashkenazi) Jewish ancestry are at increased risk to have a BRCA gene mutation. These genes are the most common cause of hereditary breast cancer. In non-Jewish populations, 1 in 500 individuals has a BRCA gene mutation. Among individuals with Jewish ancestry, one in 40 has a BRCA gene mutation.

Family History of Breast Cancer

  • Women who have close relatives with breast cancer (for example, sister, mother) have a higher risk. The risk increases if relatives are diagnosed at younger ages and if there are multiple relatives diagnosed.
  • In some families a specific gene change can be found that explains why they have more cancer in their family. Identifying a genetic mutation can clarify who in the family is at risk and what that risk is.
  • Breast cancer can be inherited from either the mother’s or the father’s side of the family.

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Gender

The strongest risk factor for breast cancer is gender. Breast cancer is about 100 times more common in females than males. This is probably because men do not have as much estrogen or progesterone in their bodies.

Genetics

About 5 to 10 percent of all cancers are caused by an inherited gene mutation. These gene mutations tend to be passed down from generation to generation. Therefore, learn as much as you can about your family history on both your mother’s and father’s sides of the family. Breast cancer is just as likely to be inherited from your father’s family as it is from your mother’s family.

Although the BRCA1 and BRCA2 genes are the most common hereditary breast cancer genes, there are many different genes that have been associated with an increased risk for breast cancer. The cancer genetic counselors at UT Southwestern can evaluate your family history to determine if you need to be evaluated for other rare genes related to hereditary breast cancer. 

BRCA1 and BRCA2 – Mutations in BRCA1 and BRCA2 account for more than half of all hereditary breast cancer. In addition to having a high risk for breast cancer, individuals with BRCA1 or BRCA2 mutations have a high risk to develop ovarian cancer. There is also an increased risk to develop other cancers, including pancreatic cancer.

BRCA gene mutations are more common among individuals with Ashkenazi Jewish ancestry. BRCA1 and BRCA2 gene testing should now include both gene sequencing and rearrangement testing (BART). Rearrangements in the BRCA genes are more common if you are of Hispanic or Middle Eastern descent. 

CDH1 – CDH1 gene mutations cause hereditary diffuse gastric cancer. Individuals with CDH1 mutations have a high risk of developing stomach cancer at a young age. In addition, women with these mutations have a high risk to develop lobular breast cancer. If you have a family history of lobular breast cancer and stomach cancer, you may need testing for this rare gene. 

CHEK2 – People who have CHEK2 mutations have an increased risk to develop breast cancer. Men may be at increased risk to develop prostate cancer. People with CHEK2 mutations also may be at increased risk to develop colon cancer and other cancers.

PALB2 – People born with PALB2 mutations are at increased risk for breast cancer. The PALB2 gene is related to pancreatic cancer as well.  If you have a family history of both breast and pancreatic cancer, you may need to be tested for this gene.

PTEN – People with PTEN mutations have Cowden syndrome. They are at increased risk to develop cancers of the breast, uterus, thyroid, kidneys, and colon. There are also some non-cancerous physical features that are unique to Cowden syndrome. 

TP53 – When this gene is mutated, it causes a rare disorder called Li-Fraumeni syndrome. Individuals with Li-Fraumeni syndrome tend to develop cancers in young adulthood and in childhood. These include cancers of the adrenal gland, brain, breast, bones, and blood. Any woman with breast cancer under the age of 30 needs to be evaluated for the TP53 gene if her BRCA gene testing is negative

STK11 – These gene mutations cause Peutz-Jeghers syndrome. Individuals with Peutz-Jeghers syndrome are at increased risk to develop breast, colon, and pancreatic cancer. They are also more likely to have unique-looking freckles around their mouth and fingers.

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Lobular Carcinoma In Situ (LCIS)

Women with LCIS have a high risk to develop breast cancer in the same breast or the opposite breast. LCIS is a condition when abnormal cells form in milk glands (lobules).

Menstrual Periods and Menopause

Women who get their periods at younger ages (younger than 12), and women who go through menopause at older ages (older than 55), are a little more likely to develop breast cancer in their lifetime. Researchers think these factors increase women’s risk because these women will have more menstrual cycles during their lives. Women who have more cycles are exposed to more hormones during their lifetimes.

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Non-Cancerous Breast Conditions

Women who have conditions such as atypical ductal hyperplasia (ADH) or atypical lobular hyperplasia (ALH) have an increased risk to develop breast cancer. This risk is about four to five times the average woman’s risk. The risk is even higher if there is a family history of breast cancer.

Breast conditions such as sclerosing adenosis, papillomatosis, ductal hyperplasia without atypia, and complex fibroadenomas somewhat increase the risk for breast cancer. The risk is increased one and a half to two times the average woman’s risk.

Conditions such as simple cysts, mild hyperplasia, non-sclerosing adenosis, mastitis, ductal ectasia, fat necrosis, hamartomas, lipomas, and fibrocystic disease are not believed to be associated with breast cancer risk.

Previous Chest Irradiation

Women who have had radiation therapy to their chest (for example, treatment of Hodgkin’s lymphoma) are at increased risk for breast cancer.

The risk is greatest for women who have had radiation during puberty. Radiation at older ages does not appear to increase the risk. If chemotherapy was given during radiation, the risk would be lower, since hormones created by the ovaries would have been stopped.

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