Breast Cancer Risk Is Not So Easy to Figure Out

Video: What Is Breast Cancer?

The U.S. Preventive Services Task Force's controversial new breast cancer screening recommendations are specifically for women who are at "normal" risk of breast cancer. But how do you know if you have a higher than average risk and thus should be more inclined toward getting screened in your 40s or should even follow special guidelines for breast cancer screening that go beyond what's usually recommended?

Some people are clearly at higher risk. The task force specifically singles out women who have a known genetic mutation—such as mutations in the BRCA1 and BRCA2 genes (as well as less common inherited problems like Li-Fraumeni syndrome)—or a history of chest radiation (a part of treatment for a childhood bout with cancer) as falling outside the scope of its "normal risk" recommendations. M. D. Anderson Cancer Center has its own detailed screening guidelines and puts women with other characteristics into the higher-risk group. Among them: women with a history of lobular carcinoma in situ—abnormal cells in the breast lobules, the milk-producing part of the breast. (LCIS is similar to ductal carcinoma in situ, or DCIS, which is not on M. D. Anderson's list.) Memorial Sloan-Kettering Cancer Center's risk-based screening recommendations say a history of atypical hyperplasia, a kind of benign breast disease, is among the factors that put women at higher risk.

Both M. D. Anderson and the American Cancer Society also describe risk in terms of the odds of getting breast cancer over a certain period of time. M. D. Anderson's high-risk group includes women with a five-year risk of breast cancer of 1.7 percent or greater at age 35 or older. How do you know if you are among them? The tool used is called the Gail model; it takes a woman's answers to questions about her family history, age at first menstrual period, and the number and characteristics of any breast biopsies, among other things, and gives an estimate of the five-year risk. Those individual factors all affect the risk of breast cancer, but they're not good at predicting risk on their own; that's why they're combined into a single algorithm, says Julie Gralow, director of breast medical oncology at Seattle Cancer Care Alliance.

The Gail model isn't perfect, though. It's good at estimating risk across large populations, but not so great at predicting whether or not an individual woman will get the disease—which, of course, is what women are concerned about! Gralow says it's particularly unhelpful when it comes to people with a family history of breast cancer, since it asks about breast cancer cases only among first-degree relatives (mother, sister, and daughter). That means it may miss noteworthy cases of breast cancer on the father's side of the family.

Family history is indeed a considerable factor in assessing women for their risk of breast cancer. It's tough to figure out your familial risk on your own, but red flags include multiple cases of breast cancer on one side of the family tree, says Mary Daly, chair of the clinical genetics department and founder of the Margaret Dyson Family Risk Assessment Program at Fox Chase Cancer Center in Philadelphia. (Breast cancer in both your mother's sister and maternal grandmother, for example, is more worrisome than an aunt with the disease on both your mother and father's side.) Other possible signs of some kind of inherited predisposition: cases of both breast and ovarian cancer on the same side of the family, or of bilateral cancers (in both breasts or both ovaries). And age of onset is important—the earlier the cancer was diagnosed, the more significant. "We also have to take into consideration how big the family is," says Daly; a pattern is statistically more likely to reveal itself in a large family than a small one. Memorial Sloan-Kettering's recommendations say that a woman even with one first-degree relative with breast cancer falls into a higher-risk category.