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The recent 29-year follow-up analysis of the prospective Swedish Study of Tabar and colleagues [1] fueled the hope that mammographic screening can reduce breast cancer mortality. The study deserves careful scrutiny given the enormity of the societal costs involved. 


The study compared the number of first breast cancer cases diagnosed over a 7-year screening period and the subsequent number of deaths from breast cancer over a 29-year follow-up period between an actively screened population (ASP) and a passively screened population (PSP). The actively screened population consisted of 77,080 women age 40–74 years at enrollment, who were offered an initial mammogram followed by a re-screening mammography every 24 months up to age 49 and every 33 months after age 49 up to age 74 years. Of the 77,080 women enrolled and offered screening, 85% attended the screenings. The passively screened population (PSP) was comprised of 55,985 demographically matched women, who were not offered mammography screening. No screens were performed after age 75. After 29 years of follow-up, the number and ratio of women from each group that had been diagnosed with breast cancer during the 7-year screening phase and of those who died of breast cancer during the subsequent 29 years of follow-up were compared.  


Breast cancer was found in 1.8% of the women studied in each group. In the ASP (the group that was offered screening), as expected, more breast cancers were diagnosed in the women who actually opted for screening. Of those 85%, breast cancer was found in 2.18%. Overall, 1426 women were diagnosed with breast cancer in the ASP during the initial 7-year period; 351 of these (24.6%) had died of breast cancer after 29 years of follow-up. This death rate of 24.6% appeared much lower than the rate in the unscreened group (PSP), where 367 of 1042 diagnosed cases (35%) had died of breast cancer. Comparing cumulative cases of death in the ASP and the PSP, the authors also calculated the ‘number needed to test’ (NNT) to ‘save one life’ and suggested this number was either 414 or 519, depending on which adjudicating source (local or overview) was used to calculate cause of death.


The insightful comments of both Amos Pines and Syd Shapiro in [i]Menopause Live[/i] on NNT [2] help to focus on the importance of measuring longevity benefits of widespread mammographic screening with and without considering oophorectomized women’s additional risks. They also addressed the importance of reporting absolute risk rather than relative risk. We agree with them wholeheartedly that risks need to be expressed in a way that patients and providers can actually understand.  

We offer an additional observation regarding screening and a comment on routine oophorectomy at the time of hysterectomy that we think are relevant to the discussion on how we should advise our patients.


  • Winnifred Cutler
    Athena Institute for Womens Wellness, Chester Springs, PA, USA
  • Regula Burki
    Department of Obstetrics & Gynecology, Hislanden Hospital, Switzerland
  • James Kolter
    Department of Obstetrics & Gynecology, Hislanden Hospital, Switzerland


  1. Tabár L, Vitak B, Chen TH, et al. Swedish Two-County Trial: impact of mammographic screening on breast cancer mortality during 3 decades. Radiology 2011;260:658-63.
  2. Pines A, Shapiro S. NNT, number needed to treat: does it have a real value? Menopause Live, 26 September, 2011.
  3. Jorgenson KJ, Gotzche PC. Overdiagnosis in publicly organized mammography screening programmes: systematic review of incidence trends. BMJ 2009;339:1-8.
  4. Santen RJ, Allred DC, Ardoin SP, et al. Postmenopausal hormone therapy: an Endocrine Society scientific statement. J Clin Endocrinol Metab 2010;95(Suppl 1): S16.
  5. Kalager M, Zelen M, Langmark F, Adami H-O. Effect of screening mammography on breast-cancer mortality in Norway. N Engl J Med 2010;363:1203-10.
  6. Garcia CR, Cutler WB. Preservation of the ovary: a reevaluation. Fertil Steril 1984;42:510-14.
  7. Cutler WB. Oophorectomy at hysterectomy after age 40? A practice that does not withstand scrutiny. Menopause Management 1996;5:10-14.
  8. Parker WH, Broder MS, Chang E, et al. Ovarian conservation at the time of hysterectomy and the long-term health outcomes in the Nurses Health Study. Obstet Gynecol 2009;113:1027-38.
  9. Elective and risk-reducing salpingo-oophorectomy. ACOG Practice Bulletin Number 89, January 2008.

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