Know your risk

Almost everything on this site is written for average risk. If yours is higher, the schedule changes — and a number is how you find out which group you are in.

Why the number matters

The American Cancer Society says women at high risk should have a breast MRI and a mammogram every year, usually starting at age 30. One of the things that puts you in that group is a lifetime risk of about 20% to 25% or greater. That is what a risk score is for. It is not trivia; it decides what screening you should be getting, and at what age.

You may already be in that group without doing any calculation

The ACS counts you as high risk, whatever a calculator says, if you have a known BRCA1 or BRCA2 change; a first-degree relative with one and you have not been tested yourself; had radiation to the chest before you were 30; or have Li-Fraumeni, Cowden or Bannayan-Riley-Ruvalcaba syndrome, or a first-degree relative with one of those. If any of that is you, take it to your doctor rather than to a website.

The two tools, and what each one is for

Tyrer-Cuzick (IBIS) — the one that answers the screening question Takes a full family history on both sides, including aunts and grandmothers, and factors in breast density. That is why breast imaging centers use it to decide whether someone crosses the 20% line. You get your risk over the next ten years and over your lifetime, plus a report you can download and hand to your doctor. Free, no sign-up. Built at Queen Mary University of London, and hosted by MagView. Open the Tyrer-Cuzick tool

NCI Breast Cancer Risk Assessment Tool — a quick picture Also called the Gail model. About five minutes. Uses your own history plus breast cancer in your first-degree relatives only — mother, sisters, daughters — and gives your risk over five years and up to age 90. The ACS says the tool used for the MRI decision should also count second-degree relatives — aunts and grandmothers — which this one does not. Useful for a general picture, but it is not the one that settles screening. Open the NCI tool

What to have on hand before you start

Both tools stall if you do not know your own details, so it is worth gathering these first. Your age, height and weight. The age your periods started, and whether you have been through menopause. Whether you have given birth, and your age the first time. Any hormone replacement therapy, and when you stopped. Whether you have had a breast biopsy and what it showed — hyperplasia, atypical hyperplasia and LCIS are each asked about separately. Whether you have had BRCA testing and what it found. And for family history: who, which cancer, and at what age they were diagnosed — on both sides, including aunts and grandmothers. If your mammogram report mentions breast density, the IBIS tool will take that too.

When these tools do not apply to you

The NCI says plainly that its tool cannot accurately estimate risk for women carrying a BRCA1 or BRCA2 mutation, or for women with a previous invasive or in situ breast cancer — and that includes DCIS and LCIS. Tyrer-Cuzick says the same: if you have been diagnosed, do not use it. If that is you, the number is not yours to calculate. Your team works from what actually happened to you.

The NCI also notes the tool is validated for women in the United States who identify as White, Black or African American, Hispanic, and Asian and Pacific Islander; that it may underestimate risk in Black women who have had previous biopsies and in Hispanic women born outside the United States; and that estimates for American Indian and Alaska Native women are based partly on data for White women and may be inaccurate.

And one thing the NCI says that is worth carrying with you: these numbers cannot say which woman will develop breast cancer. Some women who never develop it have higher estimates than some women who do. A low number is not a promise, and a high one is not a sentence. It is a reason to have a specific conversation.

Sources: National Cancer Institute — Breast Cancer Risk Assessment Tool; American Cancer Society — screening guidelines; the IBIS / Tyrer-Cuzick model, Queen Mary University of London; the Tyrer-Cuzick calculator, MagView.