Breast Cancer Risk and Prevention
Breast cancer is one of the most common cancers in women. About 1 in 8 women will develop breast cancer in their lifetime. This means there is about a 12% lifetime risk, or about 12 out of 100 women will get the disease. This means the other 88 women will not. Men are also at risk of breast cancer, but this risk is much lower than it is for women. This article will talk about breast cancer risk and prevention in women only.
Some risks for breast cancer can be modifiable, meaning you can change them (diet, weight, exercise, alcohol use, etc). Others are nonmodifiable, meaning they can’t be changed (age, family history, starting your period at a young age).
Risk factors can increase your chance of breast cancer, but they do not mean that you will definitely develop cancer. About 70% of the women who get breast cancer do not have any risk factors and more than 85% have no family history of the disease. Because of this fact, all women should talk about screening for breast cancer with their providers.
The following are risk factors for breast cancer and ways you can lower your risk of the disease.
The risk of breast cancer is higher as you get older. More women get breast cancer in their 60s and 70s than in their 30s or 40s.
Your Health History
Your health history can raise your breast cancer risk:
- Women who have their first menstrual period before age 12, or who go through menopause later (after age 55), have a slightly higher risk of breast cancer. This is thought to be from a longer lifetime exposure to estrogen in their bodies.
- Some studies have shown that breastfeeding can slightly reduce risk. This may be related to the number of menstrual periods and estrogen levels in your body.
- The age of a woman at her first live birth of a child can affect risk, but the effect depends on the number of first-degree relatives who have been diagnosed with breast cancer. For women with 2 or more 1st-degree relatives (mother, sister) with a diagnosis, their risk decreased with an older age at first live birth. For women with no family history, the risk increases with older age at first live birth.
If you have had a breast biopsy, your risk is higher. Two biopsy results have more effect on risk. Atypical hyperplasia is not a cancer but increases the risk of breast cancer by 3-5 times. Lobular carcinoma in situ (LCIS) are cancer cells found only in the lobules in the breast tissue. LCIS is not treated like other breast cancers but you will be watched closely for cancer and you may have to take medication to lower future risk. Having LCIS means your risk of breast cancer is 7 to 11 times higher than an average woman.
Women who have had a biopsy showing atypical hyperplasia or LCIS should have screening every year with mammography and exams by a healthcare provider 1-2 times a year. Some women may also have MRIs for screening. Your care team may recommend drug therapy (tamoxifen or raloxifine, discussed below) to lower your chance of breast cancer or to take part in a clinical trial. You should talk about these options with your provider.
The Breast Cancer Risk Assessment Tool looks at many of these above health factors, especially history of biopsy, and comes up with an estimated risk of developing breast cancer in the next 5 years and in your lifetime. The results are based on the Gail Model which figures out risk. Learn more about the Model or use the tool.
Hormone Replacement Therapy
Hormone replacement therapy (HRT) was often prescribed for menopausal women to reduce hot flashes, vaginal dryness, risk of bone fractures, and risk of heart disease.
- In 2002, research found that HRT was doing more harm than good and changed healthcare providers' practice.
- The Women's Health Initiative (WHI) found that taking HRT (estrogen combined with progestin) leads to a higher risk of breast cancer, heart disease, stroke, and blood clots.
- While HRT did reduce bone fractures from osteoporosis and lead to fewer colorectal cancer cases, the risks far outweighed these benefits.
- Around the same time, the HERS study found that taking HRT caused no change in heart attacks in older women with heart disease.
- A few years later, the WHI study also found that taking estrogen alone (for women without a uterus) led to an increased risk for stroke and blood clots and no change in heart disease.
- A follow-up study confirmed that women who take HRT for longer than 5 years double their annual risk of breast cancer. The study did find that after stopping HRT, the risk decreases by a lot.
Healthcare providers now suggest that women take HRT only in the lowest possible doses, for the shortest time possible. The WHI still follows the participants to watch for any long-term risks caused by HRT.
If you have taken HRT in the past, be sure your healthcare providers know that you did, and for how long. You can check on the WHI website to learn about study updates.
Birth Control Pills & Cancer Risk
Birth control pills (BCPs) first came out in the 1960s and are the most common method of contraception in the United States. Since then, the ingredients and doses of BCPs have changed. Early BCPs had 150 micrograms of ethinyl estradiol, whereas today's BCPs have about 20 micrograms. These changes make it hard to apply the results of previous studies to today's BCPs.
- In 2005, the International Agency for Research on Cancer released a report calling BCPs carcinogenic (cancer-causing). However, many of the studies used in this research were looking at older, higher-dose forms of BCPs. They found a small increased risk of breast cancer for current users and for 9 years after users stopped BCPs, after which there was no increased risk. They also found that BCPs decreased the risk of endometrial and ovarian cancer and possibly colon cancer.
- More recent studies of modern BCP doses have found no increase in breast cancer risk among current or former users. It is not known whether the newer forms of BCPhavethe same effect on endometrial and ovarian cancers.
- Recent studies have not found a higher risk of breast cancer in women with a strong family history or carriers of genetic mutations (BRCA1/2) who take or have taken BCPs.
Increased screening is not needed for women who have taken birth control pills.
Learn more from the National Cancer Institute.
Family History of Breast Cancer
Your risk partly depends on how closely related you are to family members with cancer and at what age the woman in your family was diagnosed.
- If you have a first-degree relative (sister, mother, daughter) with a breast cancer diagnosis, your risk is double that of someone without a family history.
- Having 2 first-degree relatives with the disease increases the risk about 3-fold.
- If your father or brother has had male breast cancer, your risk is also increased, though to what degree is not clear.
- If you are someone with a first-degree relative(s) with the disease, you may need to begin screening mammograms at an earlier age than the ACS guidelines of 40. Talk about this history with your healthcare providers to find out if there are any red flags for hereditary cancer syndromes. Ask your provider if you should see a genetic counselor to talk about genetic testing.
If you have a more distant relative with breast cancer, your risk becomes less certain. If your family history has a few people diagnosed with the same cancer or diagnosed before age 50, you should talk with a genetic counselor. If not, standard screening is often recommended (mammogram every year, beginning at age 40). Talk to your provider about when you should start screening.
Personal History of Breast Cancer
If you have had breast cancer in the past, you are 3 to 4 times more likely to develop another breast cancer compared to a woman who has never had the disease (not metastases or spread from the first cancer, but a new cancer). This new cancer may happen in the same breast or the other breast. It is important to keep follow-up appointments with your oncology team and continue recommended screening tests.
About 5-10% of breast cancers are inherited (or hereditary), meaning that a damaged (mutated) gene was passed down from a parent to a child. BRCA 1 & 2 are the most common and well-understood mutations, but they are not the only ones that can increase breast cancer risk. You can read more about other genetic mutations in our article Genetic Testing for Familial Breast Cancer.
You should talk with a genetic counselor if you are worried about your family history. You should be screened if you have any of the following:
- Multiple family members who have been diagnosed with breast or ovarian cancer, especially before age 50.
- Family members who have had bilateral breast cancer (in both breasts).
- Both breast and ovarian cancer is present in the family.
- There are any cases of male breast cancer in the family.
- In addition to breast cancer, family members on the same side of the family who have had prostate cancer (at a young age), colorectal cancers, stomach cancer, pancreatic cancer, and endometrial cancer.
- Your family is of Ashkenazi Jewish heritage.
BRCA1/BRCA2 Genetic Predisposition
The most common cause of hereditary breast cancer is an inherited mutation in the BRCA1 or BRCA2 gene. If you have inherited a mutated copy of either gene from a parent, you have about a 40-85% chance of developing breast cancer during your lifetime. People with these mutations tend to develop cancer at a younger age (before age 40) and these cancers more often affect both breasts. People with these inherited mutations also have a higher risk of other cancers, like ovarian cancer, male breast cancer, pancreatic cancer, and prostate cancer. BRCA mutations occur more in people of Ashkenazi Jewish (Eastern European) descent, as well as Norwegian, Dutch, and Icelandic populations, but they can happen in any racial or ethnic group.
If you know that you have a BRCA 1 or BRCA2 mutation, you should talk to a healthcare provider to make sure you have the proper screening or treatment (chemoprevention) to lower the chance of cancer or to find cancer earlier when treatment is most effective. Your healthcare provider may suggest getting mammograms at a younger age, special breast and/or ovarian cancer screening tests, or other interventions, like prophylactic (preventative) surgery or chemoprevention.
Diethylstilbestrol (DES) Exposure for Mothers & Daughters
Diethylstilbestrol (DES) was the first synthetic (manmade) estrogen and was given to pregnant women from 1938 to 1971. It was thought to prevent miscarriages and promote "healthy pregnancies." Not only did the drug not prevent problems with pregnancy, but it also caused health issues for the women taking it, as well as children born of these pregnancies. Women who took DES and their daughters have been found to be at higher risk of breast cancer.
Learn more about this risk and recommendations for screening.
Previous Chest Radiation
Women who had radiation therapy to the chest area as treatment for another cancer (like Hodgkin disease) have a much higher risk of breast cancer. The exact risk depends on the age at which they were treated. Risk is highest for those treated as adolescents, while breast tissue was developing. Treatment after age 40 does not seem to increase breast cancer risk. For Hodgkin's disease survivors who had radiation to the chest or axilla (armpit area), recommendations are:
- Annual breast exam by a healthcare professional, and monthly self-breast exam.
- Begin annual mammograms 8-10 years post-therapy.
- Breast MRI, in addition to the annual mammogram.
Speak to your provider about when you should start mammograms and breast MRI as screening.
Alcohol Use and Breast Cancer Risk
Alcohol can also increase your risk of many types of cancer, including breast cancer. Alcohol seems to increase the levels of estrogen in the body and can increase the risk of hormone positive breast cancer (also called ER+ or PR+).
Heavy drinkers are 10-15 times more likely to develop a cancer than those who do not drink. However, the overall risk increases after just 1 drink a day for women or 2 for men. (A drink is defined as 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80-proof liquor.) Higher breast cancer risk has been linked with just 3 drinks a week, so the risk is not limited to heavy drinking. Women who have 2 alcoholic drinks a day are 1.5 times more likely to develop breast cancer than a woman who never drank alcohol.
Learn more about how alcohol causes cancer and resources for quitting at the American Cancer Society.
How to Reduce Breast Cancer Risk
The Prevention Triangle: Diet, Activity & Healthy Weight
A healthy diet, regular physical activity, and keeping a healthy weight has been shown to reduce cancer risk. This triangle is thought to be the second most important step, after not smoking, in preventing cancer. Being overweight and having a diet high in fat is related to breast cancer. Research has also shown that being overweight increases the risk of recurrence in a woman who has had breast cancer.
Learn more about how the prevention triangle can help to prevent breast cancer.
Chemoprevention is the use of medications to prevent cancer. Tamoxifen was the first chemoprevention medicine to receive FDA approval. The Breast Cancer Prevention Trial showed that tamoxifen reduces a pre-or post-menopausal high-risk woman's chances of breast cancer by as much as one-half.
Tamoxifen only affects tumors that are estrogen receptor positive (ER+). There is no effect on tumors that are estrogen receptor negative (ER-). Side effects of tamoxifen include increased risk of endometrial cancer and blood clot formation. It can also increase the risk for osteoporosis in pre-menopausal women.
Raloxifene is another selective estrogen receptor modulator (SERM) that can prevent breast cancer in postmenopausal women. This medication is also used to prevent and treat osteoporosis. Raloxifene also works by blocking estrogen's effects in the breast and other tissues but seems to have fewer risks than tamoxifen. Raloxifene doesn't exert estrogen-like effects on the uterus, so there is no increased risk of endometrial cancer.
The National Surgical Adjuvant Breast and Bowel Project studied both tamoxifen and raloxifene for breast cancer chemoprevention in the STAR trial. Women took either tamoxifen or raloxifene daily for five years. The results showed that tamoxifen and raloxifene both reduced the risk of invasive breast cancer in high-risk women by about 50%.
Aromatase inhibitor (AI) medications are being studied for chemoprevention. Examples of AIs are Anastrozole and Exemestane. Studies found that women taking AIs were less likely to develop another cancer. Neither raloxifene or aromatase inhibitors were studied in women with BRCA 1 or 2 genes, so it is not clear how well they work in these women.
The decision to use a chemopreventive agent is personal and you should talk with your healthcare provider about the risks and benefits of this therapy.
Your risk of breast cancer and screening recommendations will depend on your personal history and goals. Talk with your provider about your personal risk and your options for screening.
American Cancer Society. Deciding Whether to Use Medicine to Reduce Breast Cancer Risk. 2019.
FORCE. Breast Cancer Chemoprevention. 2019.
BreastCancer.org. Breast Cancer Risk Factors.