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Many of us take it as a given that mammography reduces mortality from breast cancer. In September, 2010, Kalager and colleagues reported that, with the widespread onset of mammographic screening, there has been a calculable reduction in breast cancer mortality after diagnosis in Norway [1]. This important study shows that the reduction in mortality is not as great as had previously been estimated by the World Health Organization. The authors compared the data from the 1985–1995 historical period to the data from the 1996–2005 recent period, among both screened and unscreened groups. Compared to the historical period, both recent groups experienced a lower mortality after breast cancer diagnosis. Among women 50–69 years old, the rate of death was reduced by 7.2 per 100,000 person-years in the screened group vs. 4.8 in the matched non-screened group. Matching current (screened vs. non-screened) groups to historical groups improves our understanding of the difference between [i]mammogram screenings coupled to improved medical care[/i] vs. [i]improvements in care without mammograms[/i]. Subtracting the 4.8 rate from the 7.2 rate reduces the benefit of mammogram screening to 2.4 or, as the authors said, two-thirds of this reduction in mortality after breast cancer diagnosis is independent of mammogram screening and is apparently due to improved medical care.

Author(s)

  • Winnifred Cutler
    Athena Institute for Womens Wellness, Chester Springs, PA, USA
  • Regula Burki
    Department of Obstetrics & Gynecology, Salem-Spital, Hirslanden Hospital Group, Berne, Switzerland

Citations

  1. Kalager M, Zelen M, Langmark F, Adami HO. Effect of screening mammography on breast-cancer mortality in Norway. N Engl J Med 2010;363:1203-10.
    http://www.ncbi.nlm.nih.gov/pubmed/20860502
  2. Zahl PH, Maehlen J, Welch HG. The natural history of invasive breast cancers detected by screening mammography. Arch Intern Med 2008;168:2311-16.
    http://www.ncbi.nlm.nih.gov/pubmed/19029493
  3. Zackrisson S, Andersson I, Janzon L, Manjer J, Garne JP. Rate of overdiagnosis of breast cancer 15 years after end of Malmo mammographic screening trial: follow-up study. BMJ 2006;332:689-92.
    http://www.ncbi.nlm.nih.gov/pubmed/16517548
  4. Jorgensen KJ, Gotzche PC. Overdiagnosis in publicly organized mammography screening programmers: systematic review of incidence trends. BMJ 2009 Jul 9;339:b2587.
    http://www.ncbi.nlm.nih.gov/pubmed/19589821
  5. Santen RJ, Allred DC, Ardoin SP, et al. Postmenopausal hormone therapy: an Endocrine Society Supplement: J Clin Endocrinol Metab 2010;95(Suppl 1):S1-66.
    http://www.ncbi.nlm.nih.gov/pubmed/20566620
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