Editors note: This story originally ran Oct. 1, 2018 and was updated June 16, 2023.
It’s a sobering statistic: 1 in 8 women will develop breast cancer. It’s the most-diagnosed cancer in women besides skin cancer and the second-leading cause of cancer deaths for women in the United States.
“Breast cancer is very common and, if caught early, very treatable. It’s hard to say why an individual gets breast cancer. A mix of genetic and environmental factors is to blame,” says Melissa Troester, PhD, professor in the Department of Epidemiology and director of the UNC Center for Environmental Health and Susceptibility. “There are steps each woman can take to reduce her individual risk.”
Here’s what to know.
Uncontrollable Risk Factors for Breast Cancer
It may feel like common sense, but being a woman is the biggest risk factor.
“Ninety-nine percent of breast cancer cases are found in women,” Dr. Troester says. “However, it is important to mention that while it is rare, men can get breast cancer as well.”
Another leading risk factor is age. As a woman gets older, her risk of getting breast cancer increases. Most women who get breast cancer are 50 or older, but younger women get it, too; nearly 1 in 10 cases of breast cancer in the United States are found in women younger than 45.
Family history is another key risk factor that a woman can’t control. If a woman has a family history of multiple relatives developing breast or ovarian cancer, especially at younger ages, she’s at increased risk, Dr. Troester says. About 5 to 10 percent of breast cancers are hereditary, which means they result from a gene mutation you get from a parent.
Other risk factors include having dense breast tissue, having certain non-cancerous breast conditions, starting periods before age 12 and going through menopause after age 55.
Risk Factors for Breast Cancer That a Woman Can Control
Controllable risk factors include what you drink, what you weigh, how much you move and whether you smoke.
Research has shown that drinking alcohol increases breast cancer risk, even for women who drink moderately. Women who consume one drink a day increase their risk by up to 10 percent; women who drink two or three drinks a day have a 20 percent higher risk.
“Alcohol affects hormone metabolism and is associated with increases in DNA damage,” Dr. Troester says. “Alcohol is associated with increased risk of a number of different kinds of cancers.”
Another risk factor within a woman’s control, at least somewhat, is her weight. This risk is significantly higher in women who are postmenopausal. Keeping your body mass index under 25 is a good way to minimize risk.
Of course, it’s easier to maintain a healthy weight with exercise, which carries additional benefits for reducing breast cancer risk. Studies have shown that physically active women have a lower risk of breast cancer than women who do not exercise; the preventive effect appears to be even stronger after menopause. Exercise can lower estrogen levels and boost the body’s immune system, which might help account for its breast cancer-preventing powers.
Finally, women who want to reduce their breast cancer risk—and their risk of lung cancer, heart disease and a host of other potentially fatal illnesses—should quit smoking. Smoking has been shown in some studies to slightly increase breast cancer risk, not just for the smoker but also for others exposed to secondhand smoke. Whether or not it causes breast cancer, smoking is the No. 1 cause of preventable death.
If you’ve heard that oral contraceptives might increase breast cancer risk, that’s true—but it’s complicated. Studies have tied taking the pill to an increased risk of breast and cervical cancers, but also to a reduced risk of endometrial, ovarian and colorectal cancers. A 2017 study from the New England Journal of Medicine concluded that women who currently use or recently used hormonal contraceptives were at higher risk for breast cancer than women who had never used such methods, regardless of today’s modern low-hormone pills. That said, the increase in risk was small.
“Decisions about birth control are complex decisions,” Dr. Troester says. “Women must balance the real risk of an unwanted pregnancy against longer-term and much smaller risks of breast cancer.”
Women who carry and give birth to children seem to have a slightly lower risk of breast cancer, as do women who breastfeed. Some personal care products, such as hair straighteners and dyes, have been implicated in increased risk for breast cancer, Dr. Troester says.
Breast Cancer Screening and Advances in Treatment
Women at average risk should start regular mammograms at age 40. For women at higher risk of breast cancer, for example because of family history, mammograms should begin earlier. Again, a conversation with your doctor is key; 30 is a good age to broach the subject.
“Early detection is so important,” Dr. Troester says. “We see a lot of success with treating breast cancer that is detected early.”
In fact, the five-year survival rate for women with localized breast cancer is close to 100 percent; women with more advanced cancers also have many treatment options, but early detection offers the best chance of remission.
Those survival rates might be increasing because of research at UNC Health and elsewhere that has led to new understanding of breast cancer risk and progression.
“We’ve seen advances in imaging technology for early detection and increased options for immune-targeting therapies,” Dr. Troester says. “We are also treating women with chemotherapy earlier, prior to surgery in some cases, to lower risk of relapse.”
Talk to your doctor about your breast cancer risk, or find one near you.