Breast Cancer Screening: Why Less Might Be MoreFriday, June 15, 2012 - 20:34
When the U.S. Preventive Services Task Force (USPSTF) recommended against routine mammograms for women 40 to 49 years of age in its revised guidelines for breast cancer screening in November 2009, clinicians and patients alike squirmed with discomfort, and advocacy groups like The American Cancer Society dug in their heels to reject the recommendations. That’s because USPSTF basically said that less might be more when it comes to screening for breast cancer.
What Are the New Guidelines?
The new recommendations upended previous guidelines for breast cancer screening. Those guidelines called for all women to receive mammograms once yearly beginning at age 40, breast self exams, and clinical breast exams. The new guidelines, developed after a thorough review of available evidence, recommend that regular screening mammograms be given only to women ages 50 to 74, once every two years. For women aged 40 to 49, the USPSTF researchers concluded that there was little benefit to starting screening, but that women in that age group be given enough information by their health-care providers to make an informed decision about whether to start screening mammography. The Task Force members emphasized that they were recommending only against routine screening of women aged 40 to 49 years, and noted that many women may still wish to receive screening.
The USPSTF also said the breast self-exams (BSE) were not only useless, but caused more harm than good, in the form of psychological distress and unnecessary diagnostic tests. They didn’t find enough evidence for them to evaluate the effectiveness of clinical breast exams, mammography for women 75 years or older, or new technologies such as magnetic resonance imaging (MRI).
Here are the USPSTF recommendations verbatim, with the grades assigned them by the panel:
- The USPSTF recommends biennial screening mammography for women aged 50 to 74 years. Grade: B recommendation.
- The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take patient context into account, including the patient’s values regarding specific benefits and harms. Grade: C recommendation.
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older. Grade: I statement.
- The USPSTF recommends against teaching breast self-examination (BSE). Grade: D recommendation.
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination (CBE) beyond screening mammography in women 40 years or older. Grade: I statement.
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of either digital mammography or magnetic resonance imaging (MRI) instead of film mammography as screening modalities for breast cancer. Grade: I Statement.
Interpreting the Grades
To understand the recommendations, you need to know the basics of the panel’s grading system. The USPSTF bases it recommendations its assessment of benefits minus harms, called net benefit. The USPSTF will only make a recommendation if its members decide that there’s enough evidence available, and that evidence is of high enough quality, that it can be reasonably certain just how big that net benefit will be. The grade “A” is reserved for interventions that clearly have a substantial net benefit (note that the panel is a notoriously hard grader — not a single grade “A” appears in the bunch); Grade B interventions have moderate to substantial net benefit; Grade C is assigned to interventions with small net benefit; and Grade D is assigned to interventions that have no net benefit (have harms that exceed the benefits). If the evidence just plain isn’t of high enough quality, an “I statement” is issued.
An “A” or “B” grade leads to a clear conclusion — to “offer/provide this service.” Likewise, D recommendations are rather unequivocal in their meaning: The suggestion is to “discourage the use of this service.” For I statements, the suggestion is to “read the clinical considerations section of USPSTF Recommendation Statement. If the service is offered, patients should understand the uncertainty about the balance of benefits and harms.”
But things get a little fuzzy with grade C recommendations. The panel suggests that clinicians “offer/provide this service only if other considerations support offering or providing the service in an individual patient.” And looking at the list above, you’ll recognize that the only grade “C” recommendation is the most controversial one: whether mammography should be routine for all women under 50. That means that decisions need to be made by a woman and her physician on a case-by-case basis.
Ironically, the USPSTF recommendations bring us full circle. The 2009 review of evidence confirmed what researchers have known since the first large screening trial study of mammography, which began in 1963. That trial involved 60,000 women in New York City. By 1971 the results were clear: Mammography led to a dramatic improvement in diagnosis, treatment, and mortality for women 50 and older. But it wasn’t effective for women younger than 50.
There are several reasons why younger women don’t benefit as much from mammography screening as do older women. First, breast cancer is linked to age – cancers are simply more common in older women. For every case of breast cancer detected in women ages 40-49, 556 women need to be screened – about twice as many screenings as for women ages 50-59 (294). In addition, younger women’s breasts are denser, making it more difficult to detect abnormalities in a mammogram and leading to more false positive results. Women younger than 50 account for one out of five cases of breast cancer. Yet younger women who have mammograms have more than twice the number of surgeries and more than three times as many diagnostic procedures afterward.
The effectiveness of screening on longevity also depends on the type of cancer. Not all breast cancer is created equal. Many slow-growing cancers won’t affect a woman at all during her lifetime. For instance, a mammogram may reveal an early stage of cancer in an 80 year-old woman with congestive heart failure. It’s almost a given that she will die of heart failure before she shows any clinical symptoms of the cancer. That’s the reasoning offer . However, for healthy women in their 70’s or 80’s, mammography screening may be indicated.
In other words, researchers have known almost since the inception of widespread mammography screening that women aged 50 to 74 are most likely to benefit from the screening. The USPSTF recommendations aren’t anything new. Nor is the political maelstrom they caused.
Breast Cancer Awareness Month, Version 2010
Nearly two years later, implementation of the new guidelines has been uneven, meeting with resistance from clinicians, advocacy groups, and the public. Some hospitals have simply brushed the recommendations under the rug. My hospital’s radiology department still sports a poster with a beautiful woman, breasts tastefully covered, urging all women 40 and over to “save their lives” with breast-self examinations, clinical breast exams, and annual mammograms. I live in a small town and the budget at the hospital is definitely limited, so maybe they picked up some free posters. But it’s more likely that someone there just decided they didn’t like the new guidelines, so they’re going to ignore them.
The response of other groups, like The American College of Radiology, has been downright aggressive. This week, they unveiled their new website, Mammography Saves Lives, complete with heart-warming stories from women in their forties who were diagnosed with breast cancer via a mammogram. The site is filled with dire predictions about the effects of the USPSTF 2009 guidelines, which, they claim in their Detailed ACR Statement on Ill Advised and Dangerous USPSTF Mammography Recommendations, “could reverse [the] decline in breast cancer morbidity and mortality, causing undue suffering to women facing breast cancer and their families.” The American Cancer Society is a little nicer about it, but it, too, continues to recommend screening for all women ages 40 and older, thumbing its nose at the panel’s recommendations.
I could go on. But I think you get the point – mammograms are a useful tool. But they’re not that useful for most women under the age of 50. Perhaps we need to focus the debate on screening itself — not mammograms. That’s an important clarification: The USPSTF is recommending against routine screening mammograms for all women ages 40 to 49, using the techniques we now have available. To me, this debate says less about whether women should get mammograms than about the need to develop and assess need new, non-invasive, affordable methods to prevent and screen for breast cancers. We need to learn more about what causes breast cancers — environmental factors? Genetic factors? Socioeconomic factors? Stress? Screening tests need to be accurate enough to distinguish between slow-growing and localized cancers and more aggressive, invasive cancers. They need to work in women of all ages — and all ethnicities, and they need to be widely available. That’s the real debate. It’s unconscionable that we women still must trust our breasts — and our lives — to a technology developed in 1913.