Risky Business: Breast Cancer Risk Factors and What We Know About Them
What does it mean when we say that women in the United States face a 13% lifetime risk of developing breast cancer? According to the National Cancer Institute (NCI), that lifetime risk can be thought of as the likelihood that a woman born in the United States today will develop breast cancer at some point during her life. Every woman is different, but based on current incidence rates, roughly 13 women out of every 100 born today can be expected to develop breast cancer.
While 13% might not seem high in general terms, when considered at a population-wide scale, 13 out of 100 translates to millions of people. In 2025 alone, an estimated 316,950 women will be diagnosed with breast cancer in the United States, and more than 42,000 women will die from the disease. These new cases would be additions to the millions of existing breast cancer cases, which represent a significant public health concern even as breast cancer mortality continues to decline.
But the individual risk profile for breast cancer is not so clear-cut as the broad population data might suggest. No patient is an island, and with the concurrent progress in breast cancer research and personalized medicine, never has there been so clear an understanding of how to assess and plan for the threat that breast cancer may pose to each individual depending on a multitude of factors.
The Gene Genie: Family History, Genetics, and Breast Cancer Risk
Genetic makeup can play a major factor in the risk of developing breast cancer; between 5% and 10% of breast cancer cases are hereditary. Instead of a 13% lifetime risk, women with a harmful mutation in either the BRCA1 or BRCA2 genes face a 60% lifetime risk of developing breast cancer.
By using patient datasets that continue to expand with time, scientists are creating tools that can predict individuals’ future risk of breast cancer with the hope that increased awareness of risk factors could better inform both preventative strategies and, in the event of a positive diagnosis, treatment.
In the journal Cancer Epidemiology, Biomarkers & Prevention, published by the American Association for Cancer Research (AACR), an analysis of data from patients who had been diagnosed with abnormal breast cells that could potentially develop into cancer showed that a genetic screen may predict the risk of future disease.
Lead authors Jasmine Timbres and Elinor Sawyer, MD, from King’s College London in the United Kingdom, analyzed data from women with ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS) based on how they scored on a polygenic risk score (PRS) called PRS313. This test is based on how many of 313 breast-cancer-associated mutations a patient has. Their work showed that the higher the PRS313 score in a patient with DCIS or LCIS, the more likely the individual was to develop subsequent breast cancer—about twice as likely for either opposite-breast cancer in DCIS patients or same-breast cancer in LCIS patients.
A blood test operating on similar principles is already on the market in the United States, although it screens for breast cancer risk in the general population. Approved in 2023 and available by prescription, the Invitae Common Hereditary Cancers Panel analyzes 57 genes mutations associated with increased risk for hereditary cancers, including BRCA1, BRCA2, and CDH1, the latter of which is associated with increased lobular breast cancer risk.
The NCI also offers an easy-to-use breast cancer risk tool based on the Gail model, named after biostatistician Mitchell H. Gail, MD, PhD. By analyzing a patient’s demographic information, age, and family history, the tool can provide a calculation of breast cancer risk for some patients. However, the model is not suited for some patient subpopulations, such as those who have confirmed mutations in either the BRCA1 or BRCA2 gene or who have previously received diagnoses of DCIS or LCIS.
While not explicitly tied to cancer-causing genes per se, certain inherited phenotypes can also predispose women to breast cancer if they exhibit heritable traits that are associated with greater risk for breast cancer. Other factors, such as dense breast tissue, an earlier age of onset for menstruation, and a later onset of menopause can increase the risk of developing breast cancer.
Carcinogen Dodgeball: Avoiding Risk Factors Where Possible
Though inheriting genes that predispose us to cancer is beyond our control, we can voluntarily elect to reduce exposures to carcinogenic factors where possible in our day-to-day lives. When it comes to breast cancer, manageable behavioral patterns like alcohol consumption, exercise frequency, and diet all play a role in the risk of developing breast cancer.
A recent retrospective study in Cancer Epidemiology, Biomarkers & Prevention found that, between 2008 and 2019, the number of breast cancer cases attributable to alcohol use rose from 6.6 to 8.1 per 100,000. The study from the NCI’s Carolyn Reyes-Guzman, PhD, MPH, and colleagues showed that even light alcohol exposure can increase breast cancer risk, with analysis estimating that 4,958 breast cancer cases in 2023 could be attributed to low average daily alcohol consumption—the equivalent of just one drink per day for women.
Instead of drinking, you could be chasing endorphins from more salubrious sources, such as a runner’s high or the thrill of a well-fought pickleball victory. In a study published in the AACR journal Cancer Research, Columbia University’s Mary Beth Terry, PhD, and her colleagues converted moderate and strenuous physical activity hours into metabolic equivalent totals (METs) per week and analyzed the association between weekly MET and breast cancer risk among a population of women composed of higher-than-average breast cancer family history. Compared with the lowest MET quintile, which was categorized as the inactive group, the regular exercisers in the study cohort were 20% less likely to develop breast cancer.
Healthy dietary habits also seem to inure women against the risk of developing breast cancer. A meta-analysis of studies examining diet and breast cancer found that fruit and vegetable consumption was associated with both a 9% decrease in the risk of developing breast cancer overall and a 12% decrease of developing postmenopausal breast cancer.
Though highly variable and unevenly distributed, air pollution may contribute to an increased risk of breast cancer as well, depending on the population and the size of the pollutant particles. A study of over one million postmenopausal women in Catalonia found that exposure to increased concentrations of nitrogen dioxide and both <2.5 micrometer and <10 micrometer particulate matter were associated with 5%, 3%, and 3% increases in breast cancer risk, respectively. Although air pollution exposure may probably be more difficult to control than factors such as diet and exercise, some mitigation strategies do exist, such as the use of masks or electing to remain indoors when local pollution levels are spiking.
Other risk factors for breast cancer that can be managed with lifestyle decisions include some fixtures of cancer risk—namely, smoking status and being overweight—as well as some breast-cancer-specific risk factors, like taking hormone therapy for menopause symptoms or first pregnancy after age 35 (more estrogen exposure can lead to greater breast cancer risk, which pregnancy attenuates).
Risk Management: Not Just for Professional Analysts
Alongside developments in breast cancer treatment—which have coincided with a 41% decline in the breast cancer death rate since 1992—screening has continued to provide a bulwark of protection for breast cancer. Early detection from screening accounts for 25% of all averted breast cancer deaths from 1975 to 2020.
Vigilance and self-examinations are important, but research shows that timely mammogram screenings are indispensable. A study of 432,775 women who were invited to receive mammograms as part of the Swedish Mammography Screening Programme found that the participants who did not attend their first mammogram appointment not only tended to miss subsequent screening appointments—they were also 40% more likely to die of breast cancer than those who went to their first screening. Strikingly, the breast cancer incidence between those who went to their first screening (7.8%) and those who did not (7.6%) was about the same, which indicates that the increase in mortality was most likely due to delayed detection of what might have otherwise been a more easily treatable stage of cancer.
Thankfully, most U.S. health insurance plans have been required to cover preventative cancer screening since the passage of the Affordable Care Act (ACA). Although ACA plans and many other insurers typically begin to cover mammograms at age 40, women with a known higher risk may wish to consult with their health care providers about earlier screening.
To summarize, managing the risk of being hit with a carcinogenic dodgeball is an imperfect game. Despite individuals’ best efforts to attenuate their risk level, they may well still get hit with a breast cancer diagnosis.
Even if risk can’t be eliminated, however, an awareness of risk factors is itself a form of protection against worst-case-scenario outcomes. New technologies that quantify risk by combining genetics with environmental exposures have the potential to guide screening in ways that allow health care providers to catch and treat breast cancer at its earliest stages and with the most effective approaches. As both preventative strategies and treatments for breast cancer continue to improve, though, women can look forward to a horizon that continues to lighten even as they take steps to inform themselves of the risks they may face.
Interested in learning more about breast cancer risk and advances in breast cancer research? Visit our breast cancer awareness page for more information.
