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Abstract & Commentary
Synopsis: Screening mammography before age 50 continues to be controversial.
Source: Ringash J, Canadian Task Force on Preventive Health Care. Can Med Assoc J. 2001;164:469-476.
The Canadian Task Force on Preventive Health Care neither recommends the inclusion of screening mammography younger than age 50 nor the exclusion based upon the available evidence. The Canadian Task Force on Preventive Health Care reviewed 68 articles on screening mammography of women age 40-49. Out of this literature they accepted 7 randomized clinical trials and 6 meta-analyses for critical review. They found much to criticize in the literature on this particular subject, especially the statistical power in the studies to detect a benefit in women younger than 50. Nevertheless, they concluded that the most recent evaluations of the randomized trials indicate approximately an 18% reduction in breast cancer mortality when women age 40-49 are screened with mammography. They appropriately review the effects of an increased number of mammograms in younger women. The 2 major problems include unnecessary biopsies, which range from less than 1% in Sweden to 5-9% in the United States. The second major problem is the psychological stress of being called back for further evaluation. The Task Force finally concludes that the available evidence cannot suggest that mammography should be included in the periodic health examinations of women age 40-49. At the same time, they conclude that the available evidence does not indicate that it should be specifically excluded. Thus, their final recommendation is that women age 40-49 should be informed of the current situation and assisted in their own personal decisions.
Comment by Leon Speroff, MD
I have been a strong proponent that screening mammography should begin at age 40 rather than 50. It is well recognized that breast tumors grow faster in younger women compared with older women, and therefore, screening mammography at a frequency less than every year means that more cancers will be detected late in younger women. The earlier randomized clinical trials used the frequency of every 2 years, and it’s not surprising that their results failed to demonstrate a striking benefit.
There continues to be national confusion regarding this issue. The National Institute of Health recommends against screening mammography in women younger than age 50. The American Cancer Society and the National Cancer Institute advise screening every 1 to 2 years. The reason for this confusion, as well as the conclusion of the Canadian Task Force on Preventive Health Care, is that conclusions have been based strictly on the randomized clinical trial data. The United States National Institutes of Health Consensus Development Panel in 1997 made a similar recommendation. Neither the Canadian Task Force nor the United States Panel offered any guidance as to how the clinician could assist the patient in individual decision making. This is a good example of the problems we have in this era of emphasis on evidence-based medicine when we try to make our decisions strictly by randomized clinical trial data. Many times such data are not available or the data are too limiting. A case where the data are not available, for example, is smoking and lung cancer. If we waited for data from a randomized clinical trial, we would never advocate cessation of smoking to prevent lung cancer. This situation with mammography under age 50 is an example where the randomized clinical data are too limited. There is a British trial underway randomly assigning women age 40 or 41 to annual mammography or usual care. Results are expected after 2003. Until then, we have to make individual decisions with our patients based on our medical judgment.
In my judgment, annual mammography is indicated for women younger than age 50 despite the problem of an increased number of biopsies and the psychological stress, because this is the only method we have to detect these tumors that are in fact growing faster and would be detected at a later stage with a worse outcome by having mammography later in life. We should also keep in mind that women with a first-degree relative with premenopausal breast cancer should begin annual mammography 5 years before the age of the relative when diagnosed.
Dr. Speroff is Professor of Obstetrics and Gynecology, Oregon Health Sciences University, Portland, Ore.