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Breast Cancer: Risk Factors 

What is a risk factor?

A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone’s cancer may not be known. But risk factors can make it more likely for a person to have cancer.

Things you should know about risk factors for cancer:

  • Risk factors can increase a person's risk, but they do not necessarily cause the disease.

  • Some people with 1 or more risk factors never develop cancer. Other people can develop cancer and have no risk factors.

  • Some risk factors are very well known. But there is ongoing research about risk factors for many types of cancer.

Some risk factors, such as family history, may not be in your control. But others may be things you can change. Knowing the risk factors can help you make choices that might lower your risk. For example, if an unhealthy diet is a risk factor, you may choose to eat healthy foods. If excess weight is a risk factor, your healthcare provider may check your weight or help you lose weight.

Who is at risk for breast cancer?

Risk factors for breast cancer include:

  • Sex. Breast cancer occurs nearly 100 times more often in women than in men.

  • Race or ethnicity. Caucasian women develop breast cancer slightly more often than African-American women. But African-American women tend to die of breast cancer more often. This may be partly due to the fact that African-American women often have a more aggressive type of tumor. Why this happens is not known. The risk for having breast cancer and dying from it is lower in women who are Hispanic, Native American, or Asian.

  • Older age. 2 out of 3 women with invasive cancer are diagnosed after age 55.

  • History of breast cancer. If you’ve had cancer in 1 breast, you’re at an increased risk of having it in the other breast or another part of the same breast.

  • Previous chest radiation. If you’ve had high-dose radiation to your chest, you have an increased chance of breast cancer. The risk is even higher if the exposure happened when you were a child. It’s important to remember that this involves high doses of radiation. The small doses used for breast cancer screening do not increase your risk.

  • Family history. Having a parent, sibling, or child with breast cancer increases your risk.

  • Benign breast disease. Women with certain benign breast conditions such as hyperplasia or atypical hyperplasia have an increased risk of breast cancer. The only way to know if you have benign breast disease and what kind it is by having a biopsy.

  • Diethylstilbestrol (DES) exposure. Women who took this medicine while pregnant to lower the chance of miscarriage are at higher risk. Women whose mothers took DES during pregnancy may also have a slightly higher risk. 

  • Early menstrual periods. Women whose periods began before age 12 have a slightly higher risk of breast cancer.

  • Late menopause. Women are at a slightly higher risk if they began menopause after age 55.

  • Not giving birth to a child, or giving birth to your first child after age 30. These women have a slightly higher breast cancer risk.

  • Dense breast tissue. Women whose breasts have larger areas of dense tissue on mammograms are at increased risk for breast cancer. 

  • Recent use (within 10 years) of oral contraceptives. Taking birth control pills slightly increases your breast cancer risk compared with women who have never used them. The risk may go back to normal over time after the pills are stopped.

  • Drinking alcohol. Breast cancer risk goes up if you drink just 1 glass of wine, beer, or mixed drink a day. The more you drink, the higher your risk. Limit yourself to less than 1 drink per day.

  • Long-term use of estrogen and progestin medicines after menopause. This is known as hormone replacement therapy (HRT). The hormones are most often used together. If you have had HRT for 2 or more years to relieve menopause symptoms, you may have a higher chance of breast cancer. The longer you’ve used HRT, the higher your risk. If you stop taking the medicines, your risk should go back down to normal after 5 years. Estrogen used alone may not raise your risk much or at all, unless you use it for more than 10 years. If you decide to use HRT, use it at the lowest dose and for the shortest time possible.

  • Excess weight, especially after menopause. This risk factor is complex. Research shows conflicting results about the link between weight and breast cancer. Overall, your risk of breast cancer is lower if you stay at a healthy weight with a body mass index (BMI) below 25. If you’re overweight and you get breast cancer, the excess weight also affects your chances of being cured.

Certain inherited changes in genes are another risk factor. Hereditary breast cancer accounts for about 5% to 10% of all breast cancer cases. The genes linked to breast cancer include:

  • BRCA1 and BRCA2 genes. These are tumor suppressor genes that usually have the job of controlling cell growth and cell death. When they're changed, they don't do their job correctly, and cancer tumors may grow. Changes in these genes account for most cases of hereditary breast cancer. They're linked to other kinds of cancer, especially ovarian cancer. In the U.S., BRCA changes are most common in women of Ashkenazi Jewish ancestry.

  • PTEN gene. This gene helps control cell growth and death. Inherited changes in this gene can cause a rare disorder called Cowden syndrome. People with it have a higher risk for both cancer and non-cancer breast tumors. They also tend to have tumors in the thyroid, digestive tract, endometrium, and ovaries, often at a young age.

  • TP53 gene. This is a gene that tells cells to make a protein called p53. This protein helps stop the growth of abnormal cells. Inherited changed in TP53 cause Li-Fraumeni syndrome. People with it have an increased risk breast cancer, as well as leukemia, brain tumors, and childhood sarcomas. Less than 1% of all breast cancer is thought to be related to this syndrome.

What are your risk factors?

Talk with your healthcare provider about your risk factors for breast cancer and what you can do about them. There are different tools that can be use to help estimate your risk so that you can set up the best prevention and screening plan for you. 

Online Medical Reviewer: Cunningham, Louise, RN
Online Medical Reviewer: Stump-Sutliff, Kim, RN, MSN, AOCNS
Date Last Reviewed: 9/22/2015
© 2013 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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