There’s a great deal that’s been discovered about what causes cancer, which grows when a cell’s DNA is damaged. There’s also a great deal that’s not known, like how and why that DNA gets damaged. Research suggests the causes can be genetic or environmental, or, in many cases, a combination of the two. They’re what are known as risk factors.

Some of them we can avoid; others we can’t. But knowing what they are can make us more informed and better advocates for our own health and the health of those we love.

Here’s what you need to know.

Genetic Risk Factors

Genetic risk is the contribution our genes play in our chances of developing certain diseases. They’re generally inherited or conditional, so there’s nothing we can do about them. But they can impact the chances of developing diseases like cancer. According to the National Breast Cancer Foundation, these are the genetic risks most closely associated with breast cancer.

  • Gender

    Being a woman makes you far more susceptible. Breast cancer does occur in men, but it occurs nearly 100 times more often in women.
  • Age

    Breast cancer becomes more prevalent with age. Two out of three women with invasive cancer are diagnosed after age 55.
  • Family history and genetic factors

    If your mother, sister, father or child has been diagnosed with breast or ovarian cancer, you have a higher risk of developing breast cancer in the future. Your risk also increases if your relative was diagnosed before the age of 50.
  • Personal health history

    If you’ve been diagnosed with breast cancer in one breast, you have a slightly increased risk of being diagnosed with breast cancer in the other breast or in another part of the same breast in the future. Although this risk is low overall, it's even higher for younger women with breast cancer.
  • Menstrual and reproductive history

    Early menstruation (before age 12), late menopause (after 55), having your first child at an older age or never having given birth can also increase your risk for breast cancer.
  • Certain genome changes

    Mutations in certain genes, such as BRCA1 and BRCA2, can increase your risk for breast cancer. A genetic test can determine in you have one of these gene mutations. Many people who have a family history of breast cancer decide to undergo genetic testing.
  • Dense breast tissue

    Having dense breast tissue can increase your risk for breast cancer in some women and make lumps harder to detect. If you have dense breasts, it’s important to talk with your physician about the implications.

Environmental Risk Factors

While genetic risks are outside our control, environmental risks are often behavioral and therefore more manageable. These are the chief environmental breast cancer risks according to the National Breast Cancer Foundation:

  • Lack of physical activity

    A sedentary lifestyle (one with little physical activity) can increase your risk for breast cancer.
  • Poor diet

    A diet that’s high in saturated fat and low on fruits and vegetables can increase your breast cancer risk.
  • Being overweight or obese

    Being overweight or obese increases your risk for breast cancer, particularly if you’ve already gone through menopause.
  • Drinking alcohol

    If you frequently consume alcohol, that can increase your breast cancer risk. And the more alcohol you consume, the greater the risk.
  • Radiation to the chest

    Your breast cancer risk is higher if you’ve had radiation therapy to the chest before the age of 30.
  • Hormone replacement therapy

    Taking combined hormone replacement therapy (often prescribed for menopause) not only increases your risk for breast cancer but also increases the chances it will be detected at a more advanced stage.

Despite all we know, breast cancer is still very unpredictable. While many people who develop the disease have one or more of these risk factors, 60-70% have none at all. Other people with multiple risk factors never develop breast cancer. So having or not having risk factors doesn’t necessarily determine if you’ll develop cancer. That doesn’t mean lowering your risk is a futile exercise.

Lowering Your Risk

There are a number of valuable things you can do to reduce your risk. Some are behavioral; others will require the assistance and direction of your health care provider. But according to the American Cancer Society, all can be effective.

  • Get to and stay at a healthy weight

    As we’ve noted, increased body weight and weight gain as an adult are linked with a higher risk of breast cancer, especially after menopause. So it’s best to find and stay at a healthy weight throughout your life.
  • Be physically active

    Get regular exercise. For adults that means at least 150 to 300 minutes of moderate-intensity or 75 to 150 minutes of vigorous-intensity activity each week (or a combination of the two). It’s also preferable to spread your activity across the week rather than doing more less often.
  • Avoid or limit alcohol

    It is best not to drink alcohol if you’re at risk for breast cancer. But if you do drink, have no more than 1 alcoholic drink a day. A drink is 12 ounces of beer, 5 ounces of wine or 1.5 ounces of 80-proof distilled spirits (hard liquor).
  • Consider breastfeeding

    Women who choose to breastfeed for at least several months after giving birth may also get an added benefit of reducing their breast cancer risk.
  • Avoid hormone therapy after menopause

    If you have menopausal symptoms, talk to your health care provider about treating them with non-hormonal options.

If you have a strong family history of breast cancer or a known gene mutation that increases your risk, here are some additional things to consider to help reduce your risk.

  • Genetic counseling and testing

    If you have as a strong family history of breast cancer or a family member with a known gene mutation, you might want to talk to your doctor about genetic counseling and testing, which can help determine your risk.
  • Close observation

    For women at increased breast cancer risk, having more frequent doctor visits, starting breast cancer screening at an earlier age, and adding other screening tests like breast MRI can provide peace of mind and help identify cancer earlier, when it’s easier to treat.
  • Medication

    Prescription medicines that block the action of estrogen in breast tissue can also be used to help lower breast cancer risk in certain women.
  • Preventive surgery

    For the small fraction of women who have a very high risk for breast cancer, surgery to remove the breasts may be an option. Removing the ovaries, which are the main source of estrogen in the body, is another surgical option. While surgery can lower the risk of breast cancer, it can’t eliminate it completely, and it can have its own side effects.

There are expected to be more than 275,000 new breast cancer cases in the U.S. this year. If we can prevent any of them with awareness, education and prevention, it would be a phenomenal accomplishment. So talk with your health care provider to better understand your risk, be vigilant about your breast health and take every possible precaution to keep yourself and those you love safe and healthy.