What Causes Breast Cancer? 10 Risk Factors To Know

Breast cancer is the most commonly diagnosed cancer among American women, except for skin cancers. In the United States, about one in eight women will develop invasive breast cancer in her lifetime. 

On the bright side, there are more than 4 million breast cancer survivors in the United States. Thanks to increased awareness and screening, as well as better treatments, doctors are finding breast cancer earlier.

Breast cancer risk factors

About 85% of breast cancers occur in women with no family history. There are risk factors that can increase your chance of getting breast cancer. Some of those are lifestyle-related, and others you can't control.

Breast cancer risk factors you can't control include:

• Sex: Being female is the primary risk factor for breast cancer. Male breast cancers account for less than 1 percent.
• Age: Breast cancer affects mainly middle-aged and older women. The average age at the time of breast cancer diagnosis is 62.
• Race: Breast cancer is more common in Caucasian women, but mortality is higher in African-American women due to the increased prevalence of higher risk breast cancers.
• Family history or genetic predisposition: Having one first-degree relative, such as a mother, sister or daughter, with breast cancer doubles a woman’s risk of getting the disease. Having two first-degree relatives with breast cancer increases a woman's risk by three, even without a genetic mutation. About 5% to 10% of breast cancers are thought to be hereditary and due to a genetic mutation, which can increase risk as much as 50% to 80%.
• History of abnormal biopsy: Changes in the breast increase the risk of breast cancer.

Lifestyle factors that increase a woman's risk for breast cancer include:

• Delaying childbirth until after 30
• Long-term use of combined hormone replacement therapy to treat menopause symptoms and prevent osteoporosis
• Increased alcohol consumption. Women who consume between two and five drinks daily compared to non-drinkers have about 1.5 times the risk.
• Being obese
• Smoking

Lifestyle factors that can lower your risk of getting breast cancer include:

• Breastfeeding
• Being physically active. Studies have shown that women who do between 1.25 to 2.5 hours a week of moderate physical activity, such as walking, reduces risk by 18%.

Breast cancer screening

Breast cancers do not always have symptoms and many can only be detected on screening mammograms. It is recommended that most women over 40 get yearly screening mammograms, regardless of family history.

You also should know your family history, including whether anyone in your family has ever had breast or ovarian cancer and at what age.

Women at a high risk for breast cancer may need to start screening before age 40, or they may need screenings with breast MRI to provide more detail about their breast tissue.

It's also important that you know what your breasts normally feel and look like. If you notice a change, be sure to notify your physician — even if you’ve had a normal mammogram within the year. 

What happens if I am diagnosed with breast cancer?

• Take a deep breath. This is easier said than done. Everyone reacts differently to receiving a cancer diagnosis. It is important to give yourself time to process this life-changing news.
• Meet with your doctor. The first doctor you typically meet with is a breast surgeon. This should be someone you trust and feel comfortable with. They will be with you throughout your entire journey and help guide your different treatments in coordination with the rest of your care team.
• Get the facts. There are different types of breast cancer. Depending on which type you have, the treatments can vary dramatically. Each cancer is unique and your care team will individualize your treatment accordingly. 
• Educate yourself. Patients who have educated themselves about their diagnoses are prepared for the next steps. Do not be afraid to ask your surgeon for additional resources.
• Develop a support system. The first months after a cancer diagnosis can be an emotional, mental and physical rollercoaster ride for some patients. Surround yourself with people who support and love you. Family and friends will want to help. Practice saying "yes." Let them bring you a meal, give you a ride, help with child care or run an errand for you.