On November 17, 2009, The New York Times headline read, “New Mammogram Advice Finds a Skeptical Audience.” The Wall Street Journal announced, “Breast-Screening Advice is Upended.” Similar headlines appeared in newspapers and periodicals across the country, and women who had grown accustomed to breast cancer screening protocols were suddenly wondering what to do next.
The stimulus for this furor was supplied by the U.S. Preventive Services Task Force (USPSTF), an independent panel of medical experts that conducts scientific reviews of preventive health care services and then develops guidelines for physicians who care for patients on a day-to-day basis. After an extensive review of scientific literature on breast cancer screening and its effects on cancer mortality, the USPSTF hammered out new recommendations.
U.S. Preventive Services Task Force Ratings
The USPSTF ranks its recommendations according to the quality of scientific studies or the extent of clinical experience surrounding a specific issue of preventive health care – what is popularly known as “evidence-based medicine.”
Recommendations are rated as follows:
- A: Recommendation is based on consistent and good-quality patient-oriented evidence
- B: Recommendation is based on inconsistent or limited-quality patient-oriented evidence
- C: Recommendation is based on consensus, usual practice, opinion, disease-oriented evidence or case series for studies of diagnosis, treatment, prevention, or screening
- D: USPSTF recommends against the practice
- "I" Statement: Evidence for making any recommendation is insufficient
Obviously, an “A” recommendation is based upon the strongest scientific evidence, while a "C" recommendation can be based merely upon usual and customary clinical practice, whether or not such practice is rooted in fact. A “D” recommendation is usually offered when the majority of evidence shows there is no benefit from a particular clinical practice or that such a practice actually causes harm.
Breast Screening Recommendations Based on Evidence of Inferior Weight
Surprisingly few clinical guidelines are based on clear-cut, consistent, good-quality scientific data, or "A" recommendations. This is partly due to inherent weaknesses in the structure of clinical research. Confounding variables, such as placebo effect or bias, are not always easily controlled. Nor is statistical evaluation as straightforward as one might believe.
Therefore, much of the data used by the USPSTF to formulate its recommendations for breast cancer screening is of questionable quality:
- The USPSTF recommends that women between the ages of 50 and 74 years receive a screening mammogram every two years. This is a “B” recommendation.
- The decision to start screening mammograms before age 50 should be based on a woman’s personal risk factors for breast cancer and her own values regarding the specific benefits and harms of screening. This is a “C” recommendation. The USPSTF based this recommendation, in part, on the observation that a higher number of “false positives” – mammograms that are interpreted as suspicious for cancer when no cancer is actually present – occur in women aged 40 to 49 years.
- For women over 74 years of age, there is insufficient evidence for the USPSTF to recommend for or against screening mammography – an “I” statement.
- There is insufficient evidence – another “I” statement – to assess the benefits or risks of clinical breast examination, which is a manual breast examination performed by a physician or other medical provider, in women 40 years or older.
- The USPSTF also issued an “I” statement regarding the value of performing digital mammography or breast magnetic resonance imaging (MRI) instead of traditional X-ray mammography.
- The USPSTF recommends against teaching women breast self-examination (BSE), because there is sufficient evidence to show that teaching BSE does not reduce breast cancer mortality and may even increase the risk for harm. This is a “D” recommendation.
So how does one interpret these recommendations?
The decision to get a mammogram – or to participate in any other means of breast cancer screening – rests with each woman. Such a choice can only be made in the light of full disclosure about personal risk factors for breast cancer and the potential risks and benefits of all screening modalities.
Sources
- New Mammogram Advice Finds a Skeptical Audience. The New York Times. Jennifer Steinhauer.November 17, 2009
- Breast-Screening Advice is Upended. The Wall Street Journal. Shirley Wang. November 17, 2009
- Screening for Breast Cancer: Recommendation Statement. American Family Physician. 2010;82(6):672-76
Stephen Allen Christensen - Dr. Steve Christensen's writing has appeared in magazines, professional journals, poetry anthologies, and children's books since 1976.
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