Breast Cancer: What’s Your Risk?

One in 8. By now, most women are familiar with the statistic that predicts 1 in 8 women in the United States will develop breast cancer at some point in their lives.

Julia McGuinness, MD

Julia McGuinness

Yet for many women (and people assigned female at birth), those odds are an underestimate.

“When thinking about who’s at high risk for breast cancer, women with a strong family history of breast cancer or mutations in genes like BRCA1 or BRCA2, which are associated with a 60 to 80% lifetime risk of breast cancer, probably come to mind,” says Julia McGuinness, MD, a breast cancer oncologist and assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons.

“But more commonly, breast cancer risk is influenced by a combination of different factors that might not be related to inherited mutations or family history at all.”

These other risk factors are common but underrecognized, even by physicians, McGuinness adds.

People who have a high risk of breast cancer from these factors should be screened for breast cancer more often and may want to consider preventive measures—including medication—that reduce risk.

“We can do something,” McGuinness says, “but we have to identify the patients first, and right now, risk assessment is underutilized.”

Alcohol, menopause, and other risk factors

Some of the factors that raise the risk of breast cancer are “reproductive,” including the age your period began, how old you were when menopause started, and how old you were when you gave birth to your first child.

Others are lifestyle factors that can be modified, including weight and alcohol consumption.

What all these factors have in common is estrogen. “They all affect the exposure of breast tissue to estrogen over a woman's lifetime,” McGuinness says. For example, women who’ve never been pregnant or whose periods started early have a higher risk because their breasts are exposed to estrogen for longer periods of time or without interruption.

The main source of estrogen in premenopausal women is the ovaries, but estrogen is also produced in other tissues in the body, including fat cells. “By being overweight or obese you have could have higher production of estrogen in the body, which fuels hormone receptor positive breast cancers, the most common type,” McGuinness says. Alcohol is also known to raise estrogen levels in the body, and drinking more than one drink on average per day is linked with an increased risk of breast cancer.

Other factors that raise risk include breast biopsies, even if cancer isn’t detected, increased breast density, and the presence of atypical cells on breast biopsy, such as atypical hyperplasia or lobular carcinoma in situ.

“The important thing to know is that breast cancer risk is dynamic, so can change over time,” McGuinness adds. “If you have a new biopsy, or even just by virtue of getting older, your risk increases.”

Assessment tools can calculate risk

Multiple risk assessment tools are available to physicians to estimate a woman’s risk of breast cancer, which could be used by her primary care physician. Those who meet high-risk criteria should be referred to an breast oncologist or breast surgeon who specializes in the care of high-risk women.

“We sit down with women and go through all their risk factors, and then estimate their risk based upon different models, because some underestimate risk in certain cases and some overestimate risk in others. That gives us a global picture of a patient’s risk.”

A woman is considered to have a high risk if she has at least a 1.67% chance of developing breast cancer in the next five years, or a lifetime risk of at least 20%.

Genetic testing is usually ordered if the patient has a strong family history of breast cancer, but might not be ordered in a patient without a family history in whom the probability of finding a genetic mutation associated with an increased risk of breast cancer is lower.

Screening and risk reduction

When a woman is found to be high risk, “then we usually have a discussion about what works best for the patient, based on what their risk factors are, and their overall health,” McGuinness says.

Yearly mammograms are recommended, and two other imaging options—breast ultrasound or breast MRI—may be added in.

Losing weight, eating fruits and vegetables, moderating alcohol intake, and exercising can also help reduce risk, but not dramatically.

The biggest reduction in risk is achieved with medications. Tamoxifen, which is also used by women who have breast cancer, reduces the risk of breast cancer by about 50%, if taken for five years. Other drugs called aromatase inhibitors are also effective options among women who have gone through menopause.

“These options obviously have potential side effects,” McGuinness says, “And that’s why the discussion is individualized to help women decide what's right for them.”


Julia McGuinness, MD, is assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons within the Division of Hematology/Oncology, where she specializes in the care of patients with breast cancer or have a high risk of developing breast cancer.

She serves as the principal investigator for multiple clinical trials at Columbia that evaluate novel treatments for patients with breast cancer. She is also evaluating novel imaging-based tools to refine breast cancer risk prediction and to predict which patients will benefit from breast cancer therapies.