Introduction
On Monday this week, the United States Preventive Services Task Force (USPSTF), the longstanding independent expert panel focused on prevention and primary care and whose members are appointed by the Department of Health and Human Services, released new screening guidelines raising the minimum age (from 40 to 50 years) at which adult women should start mammography screening for breast cancer, loosening the interval between such examinations from yearly to every other year, and even dispensing completely with self-examination of breasts (Kolata, 2009). The caveat is that these guidelines appeal to all but the small number of women identified as being a medium- to high risk for contracting breast cancer.
This is an authoritative pronouncement because the USPSTF is a national body tasked to furnish well-considered guidelines to doctors, insurance companies, and policy decision-makers.
Research Method and Statistical Analysis
In order to rigorously evaluate national breast cancer screening strategies (there are 20 extant) anew, the Task Force did a meta-analysis of all available studies covering the contemporary cohort of women 39 to 79 years old. A meta-analysis is a way to combine findings from separate research teams that have a common methodology. This is not as difficult as it sounds since the common methodology merely had to be prospective studies that follow and record outcomes for a cohort of American women. Cost and benefit analysis was then modeled with the help of five independent bodies such as the Erasmus Medical Center in the Netherlands, Georgetown University in Washington DC, and Stanford University in Palo Alto. Without meaning to but by virtue of common data types and data analysis comparing prevalence rates and odds ratios – akin to the discussion of probability rates in populations and samples – the five models yielded consistent rankings of screening strategy effectiveness (Mandelblatt et al., 2009; Bennett, Briggs, and Triola, 2009).
On the whole, the Task Force reports that a 15% reduction in breast cancer mortality that can be ascribed to the use of mammograms seems decidedly low compared to the risks and harm which tend to affect women in their forties more (the odds ratio is 60% higher in this age group versus females 50 or older). Moreover, women just entering middle age are much less likely to be diagnosed with breast cancer anyway. As well, the mortality rate associated with ten years of annual mammography screenings was substantially lower in early middle age (O.R. = 0.0005) compared to those aged 60 to 69 (O.R. = 0.003).
Just as valuable and eminently sensible for women is that the latest USPSTF recommendation adds the dimension of cost-benefit analysis. The Task Force points out that many women are kept in the dark about: a) the physical trauma of a mammogram procedure (one patient describes it as having her breasts squeezed by an ice-cold freezer door); b) the great number of false positives the test yields and the emotional torture this leads to; c) that trigger unnecessary follow-up tests that are not only invasive but also harmful (e.g. a biopsy); and, d) the indiscriminate rush to radical mastectomy even for breast tumor types that will never grow to a malignant mass in the average life expectancy of an American woman.
Unneeded health care expenses aside, therefore, the Task Force guideline clearly contributes to the medical profession’s precept, “first of all, do no harm” (Primum non nocere).
Appropriateness of Conclusions
Quite apart from the statistical rigor of the models relied on to support the recommendation, these very new guidelines have met an ambivalent reception. On the one hand, women just entering their forties feel a kind of reprieve that they need not feel too anxious just yet about being diagnosed with breast cancer.
Alone among the respected institutions concerned the breast cancer prevention and treatment, the National Cancer Institute admitted to keeping an open mind and deciding to at least re-evaluate NCI’s own breast cancer screening guidelines based on the newer, scientifically-derived findings. As well, advocacy groups such as the National Breast Cancer Coalition, Breast Cancer Action, and the National Women’s Health Network that invested time and effort in alerting American women to be vigilant about this second most prevalent cancer among women responded positively to the new guidelines.
However, the news story reports that the American Cancer Society and the American College of Radiology in effect repudiated the findings by their preference for continuing to recommend annual mammograms from 40 years onward. Informal polls among middle-aged women taken by newspapers like the NYT and the Washington Post showed some were taken aback by such seeming loosening of caution.
In large part, the credibility gap can be traced to the fact that a different panel of USPSTF members had found the cumulative evidence as of 2002 inconclusive and decided to recommend staying with longstanding guidelines about having annual mammograms from age 40. One assumes that the ambivalence of the general public is based on erring on the side of caution, owing to all they had learned about the high death rates associated with breast malignancies.
References
Bennett, J.O., Briggs, W.L., & Triola, M.F. (2009). Statistical reasoning for everyday life (3rd ed.). Boston, MA: Pearson Education, Inc.
Kolata, G. (2009). Panel urges mammograms at 50, not 40. The New York Times. Web.
Mandelblatt, J. S., Cronin, K. A., Bailey, S., Berry, D. A., de Koning, H. J. et al. (2009). Effects of mammography screening under different screening schedules: Model estimates of potential benefits and harms. Annals of Internal Medicine, 151 (10) 738-747.