What a breast cancer risk calculator can and can’t tell you

This week, actress Olivia Munn shared that she was diagnosed with and treated for breast cancer last year, and credited a risk calculator with helping her doctor catch the cancer early.

“Ask your doctor to calculate your Breast Cancer Risk Assessment Score,” Munn urged the public in her post.

Medical experts are enthusiastic about the spotlight on risk calculators, but they caution that the results are only rough estimates and need to be interpreted with the help of a doctor. Here’s what to know.

What do breast cancer risk calculators take into consideration?

About one in eight women will develop breast cancer in her lifetime. But tools such as the one Munn’s doctor used can offer a more personalised picture of an individual patient’s risk.

There are two main calculators: the Breast Cancer Risk Assessment Tool, also known as the Gail model, and the Tyrer-Cuzick Risk Assessment Calculator, also called the IBIS model. Both ask users their age, race, ethnicity, family history of breast cancer, when they first started their periods, and, if they have children, how old they were when they had their first child. All of these factors can influence a person’s risk of breast cancer.

The IBIS calculator also asks for information about an individual’s biopsy history, breast density and the age at which any family members were diagnosed with breast cancer.

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The calculators compare a person’s answers with the average for other women from the same age and racial group, and use that to estimate five-year risk and lifetime risk of developing breast cancer.

Although men can also develop breast cancer, the tools calculate risk only for women. The Gail model cannot accurately calculate risk for women with a history of invasive breast cancer or ductal carcinoma in situ or those with mutations in the BRCA1 or BRCA2 genes, which raise the risk of breast cancer, said Dr Sandhya Pruthi, a breast medicine specialist at the Mayo Clinic Comprehensive Cancer Center.

Accuracy can also vary for different racial groups. “These things were originally built around women from Western Europe,” said Dr Otis Brawley, associate director of community outreach and engagement at the Sidney Kimmel Comprehensive Cancer Center.

According to the National Cancer Institute, the Gail calculator may underestimate risk in Black women with previous biopsies and Hispanic women born outside the United States. It may also be inaccurate for American Indian or Alaska Native women, because data about their risks is limited. Black women can ask their doctors about the Black Women’s Health Study calculator, which was developed using data from Black women in the United States.

It is also essential to make sure that you understand the data required to answer the questionnaires and input it correctly, Dr Pruthi said. Even small changes in the answers can yield vastly different risk scores. And experts noted that these calculators should be used as part of more comprehensive care, including regular doctor appointments and recommended screenings such as mammograms. They can also be useful for women who are not yet old enough to have routine mammograms.

How do you interpret the risk score?

Breast cancer risk calculators should be used as a conversation starter with a healthcare professional, said Dr Nancy Chan, an oncologist and director of breast cancer clinical research at NYU Langone’s Perlmutter Cancer Center. Knowing your risk estimate can help you and your doctor discuss whether you might need more frequent mammograms or genetic testing, or whether certain preventive steps might help lower your risk.

“If you are high risk, we actually can do something about that,” she added. Doctors may recommend that women with a high score make certain lifestyle changes – such as exercising more, cutting back on smoking and reducing alcohol intake – or that those with a high five-year risk take medications that can help reduce the likelihood of breast cancer.

However, doctors caution that interpreting your score can be difficult on your own. The difference between the five-year risk score and lifetime risk, in particular, can be hard to understand, Dr Brawley said.

“One of the things I worry about is that a woman will run the test and come out with lower than average risk for breast cancer – say, lifetime risk of 7 per cent – and decide, ‘Oh, then I don’t need to get into a programme of routine high quality screening’,” Brawley said. Other women might get a higher risk score that, if interpreted without other context, may lead to over-testing or unnecessary anxiety.

“You don’t want people to just look at these numbers and get unduly frightened,” said Dr Steven Woloshin, a professor of medicine at Dartmouth University who has studied overdiagnosis.

A risk score cannot determine whether a person will or won’t develop breast cancer. And it does not say anything about your chances of dying from the disease, Prof Woloshin said.

Other risk assessment tools are being developed that could help doctors make even stronger predictions in the future, Dr Pruthi said. “Where we really want to be one day is getting a personalised risk,” she said. “What new information can we add that’s more unique to you?” NYTIMES