Breast cancer risk factors: age, genes, hormones and what you can change

What breast cancer is

Breast cancer starts in breast tissue, when cells in the breast change and grow out of control. It is the second most common type of cancer in women in the United States, and it can rarely affect men (MedlinePlus). A risk factor is anything that raises the chance of getting a disease. Having one or more risk factors does not mean you will get breast cancer, and some people who get it have no known risk factors (NCI).

On average, women have a 1 in 8 (or 13 in 100) chance of getting breast cancer during their lifetime (NCI).

Risk factors that raise the risk

The National Cancer Institute (NCI) groups the risk factors like this (NCI):

• Age. Besides female biological sex, getting older is the most important risk factor (NCI).
• Inherited gene changes. A harmful change in a gene linked to breast cancer, such as BRCA1 and BRCA2, PALB2, CHEK2, TP53 (Li-Fraumeni syndrome), CDH1, PTEN (Cowden syndrome), STK11 (Peutz-Jeghers syndrome) or ATM (NCI). BRCA1 and BRCA2 changes also raise the risk of ovarian and other cancers (MedlinePlus).
• Family history. A family history of breast cancer, for example in a mother, daughter or sister (NCI).
• Personal history. Having had breast cancer, ductal carcinoma in situ (DCIS) or certain other breast changes in the past (NCI). MedlinePlus also lists benign (noncancer) breast disease (MedlinePlus).
• Dense breasts. Dense breast tissue is common. It raises the risk and also makes breast cancer harder to see on a mammogram (NCI).
• Radiation. High levels of radiation in the past, especially at a young age, such as treatment for a childhood cancer (NCI), or radiation therapy to the breast or chest (MedlinePlus).
• A longer lifetime exposure to estrogen. Getting your first period early, starting menopause later, being older at your first birth, never carrying a pregnancy to term, and, among women who have given birth, never breastfeeding (NCI) (MedlinePlus).
• Menopause hormone therapy. Taking combined estrogen plus progestin hormone therapy for menopause symptoms (NCI).
• DES. Exposure to DES, a synthetic estrogen, before birth, or taking it during pregnancy (NCI).
• Excess body weight, especially after menopause (NCI).
• Alcohol. The more alcohol you drink, the greater the risk (NCI). See alcohol and cancer risk.
• Not being physically active, especially after menopause (NCI).

Race also plays a part. In the United States, White women have the highest rate of breast cancer, and Black women have the highest death rate (NCI).

Some risk factors on their own carry a very high risk, 60 in 100 or more: certain harmful changes in genes such as BRCA1, BRCA2, PALB2 and PTEN; a strong family history with several relatives diagnosed; and radiation to the chest before age 30 (NCI).

NCI says two things need more study: birth control pills (some studies show a slight rise in risk in current or recent users and others do not) and chemicals in the environment (NCI).

Which ones you can change

What lowers the risk

Nothing can guarantee you will not get breast cancer, but NCI lists these protective factors (NCI):

• Drinking less alcohol or none, and staying at a healthy weight.
• Being physically active.
• An early pregnancy. Women who have a full-term pregnancy before age 20 have a lower risk than women who have not had children or who give birth to their first child after age 35.
• Breastfeeding for at least several months after childbirth.

MedlinePlus adds limiting hormone therapy (MedlinePlus).

For people at high risk

• Risk-reducing medicines. Tamoxifen and raloxifene are FDA-approved to lower breast cancer risk in women at higher than average risk; raloxifene is used only after menopause. Aromatase inhibitors such as anastrozole and exemestane may be used after menopause but are not FDA-approved for this. These medicines have serious side effects, so the benefits and harms need a talk with your doctor (NCI). The US Preventive Services Task Force recommends that clinicians offer them to women 35 or older at increased risk who are at low risk of side effects (USPSTF 2019). See the breast cancer prevention medicine check.
• Risk-reducing surgery. Removing both breasts (risk-reducing bilateral mastectomy) is generally done only for people with an inherited change that greatly raises the risk, such as in BRCA1 or BRCA2, or a very strong family history (NCI).
• Genetic counseling. The USPSTF recommends that women with a personal or family history of breast, ovarian, tubal or peritoneal cancer, or an ancestry linked to BRCA1/2 changes, be checked with a brief family risk tool, and get genetic counseling if it is positive (USPSTF 2019). The BRCA family history check walks through it.

Changes to report

Early breast cancer often has no symptoms (NCI). Most breast changes are not cancer, but NCI says to check with your doctor about unusual changes such as (NCI) (MedlinePlus):

• A lump or thick, firm area in or near the breast or under the arm
• A change in the size or shape of the breast
• Fluid from the nipple that is not breast milk, or a nipple that turns inward, flattens or changes direction
• Scaly, swollen, red or darker skin on the breast, nipple or areola, or itching or tingling there
• Swelling of the breast even without a lump, a skin rash, or dimples or puckering

Breast cancer does not usually cause pain, but see a doctor about breast pain that does not go away (NCI). Follow up on any breast change, even if you had a normal mammogram recently (NCI).

When screening starts

The US Preventive Services Task Force recommends a mammogram every other year for women aged 40 to 74 (USPSTF 2024). The breast cancer screening age check compares this with the American Cancer Society guideline. Women who may be at higher risk can talk with their doctor about screening or prevention options (NCI). To estimate a 5-year and lifetime risk, try the breast cancer risk calculator, and see screening tests by age for the other checks for your age.

Common questions

Can I get breast cancer with no family history?

Yes. Some people who get breast cancer have no known risk factors, and age is the most important one after being female (NCI).

How exact is a breast cancer risk estimate?

Not very. NCI says doctors cannot estimate a person's risk precisely: a calculator can miss a factor that affects you, and the science changes over time, so an estimate is a best guess (NCI).

Can men get breast cancer?

Yes, but rarely (MedlinePlus).