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.
M. D. Anderson suggests that women with a strong family history of the disease consider speaking with a genetic counselor to better assess their risk (that may also include tests for specific mutations). If the risk of breast cancer is 20 percent or greater over a lifetime, you fall into the increased risk category. The American Cancer Society also says women with a 15 to 20 percent lifetime risk are at moderately increased risk.
If you are at higher than usual risk of breast cancer, you should talk to your doctor about what your best screening schedule might be. The ACS, for example, recommends that women with a 20 percent or higher risk get both a mammogram and an MRI every year (it doesn't recommend a starting age), while women in the moderate-risk category should weigh the benefits and limitations of adding MRI to an annual mammogram. M. D. Anderson's guidelines include, for example, a clinical breast exam every six to 12 months, on top of an annual mammogram, for women with a history of LCIS. Sloan-Kettering's recommendations for women with one or more first-degree relative with a history of the disease include a clinical breast exam every three to six months and an annual mammogram starting 10 years before the age at which the youngest relative with breast cancer was diagnosed. It's worth noting that breast density, which is assessed by mammogram, is also a risk factor for breast cancer. Because regular mammography is a particularly poor tool for detecting cancers in dense breasts, women with this risk factor should talk to their doctor about whether digital mammography or ultrasound may be a better option.
The tough part of all of this is that most women who get breast cancer have no significant risk factors at all, says Daly—and yet they get sick anyway. (While you may have heard that things like weight and activity level influence breast cancer risk, no one suggests that a woman who has no major risk factors other than being overweight should act differently when it comes to screening.) And most healthy women attempting to gauge their own risk will not fit into any of these defined categories.
For most women, we simply don't have the tools to predict individual risk with any confidence, says Gralow. Because of that lack of information, for most women, the discussion with her doctor about whether she should get a mammogram in her 40s, or whether it should be an annual or biennial event if she is 50 or older, is pretty much limited to how she feels about the potential harms of the test (false positives and biopsies, and also the risk of diagnosing and treating something that never would have been life-threatening) rather than whether she's more likely than the average Jane to develop the disease. Those on both sides of the debate agree that this is a big problem. "We urgently need risk models with better discriminatory accuracy (than that of current models) that can correctly identify persons at all levels of risk," wrote Karla Kerlikowske, director of the women's clinic at the Veterans Affairs Medical Center in San Francisco, in the editorial accompanying the task force report. (Both were published in the Annals of Internal Medicine.) In addition, she wrote, "healthcare systems would need to develop mechanisms for routinely assessing risk factors, calculating breast cancer risk, and reporting risk to women and providers in an easily understandable format."
Sounds great, and it would certainly make easier the mammography decision for many women. For now, though, such a comprehensive risk assessment is not available—and women still face some very difficult decisions over what to do about breast cancer screening.