Katrina Armstrong, MD, MSCE; Elizabeth Moye, BA; Sankey Williams, MD; Jesse A. Berlin, ScD; Eileen E. Reynolds, MD
The risks and benefits of mammography screening among women 40 to 49 years of age remain an important issue for clinical practice.
To evaluate the evidence about the risks and benefits of mammography screening for women 40 to 49 years of age.
English-language publications in MEDLINE (1966â€“2005), Pre-MEDLINE, and the Cochrane Central Register of Controlled Trials and references of selected studies through May 2005.
Previous systematic reviews; randomized, controlled trials; and observational studies.
Two independent reviewers.
In addition to publications from the original mammography trials, 117 studies were included in the review. Meta-analyses of randomized, controlled trials demonstrate a 7% to 23% reduction in breast cancer mortality rates with screening mammography in women 40 to 49 years of age. Screening mammography is associated with an increased risk for mastectomy but a decreased risk for adjuvant chemotherapy and hormone therapy. The risk for death due to breast cancer from the radiation exposure involved in mammography screening is small and is outweighed by a reduction in breast cancer mortality rates from early detection. Rates of false-positive results are high (20% to 56% after 10 mammograms), but false-positive results have little effect on psychological health or subsequent mammography adherence. Although many women report pain at the time of the mammography, few see pain as a deterrent to future screening. Evidence about the effect of negative screening mammography on psychological well-being or the subsequent clinical presentation of breast cancer is insufficient.
Few randomized, controlled trials assessed the risks of screening, and the literature search was completed in 2005.
Although few women 50 years of age or older have risks from mammography that outweigh the benefits, the evidence suggests that more women 40 to 49 years of age have such risks.
Numbers correspond to the risks and benefits outlined in the Table.
Appendix Table 1.
Appendix Table 2.
Appendix Table 3.
Appendix Table 4.
Appendix Table 5.
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H Lee Moffitt Cancer Center & Research Institute, University of South Florida
April 4, 2007
Estimating net benefits and harms of screening mammography in women age 40-49
In the updated systematic review on the effects of screening mammography [SM] in women age 40-49, Armstrong et al  used relative effect measures to express most important benefits of SM, while at the same time they expressed most important harms of SM in terms of absolute effect measures. Notably, they estimated that SM is associated with relative-risk reduction in breast cancer mortality of 7-23%, while 30-200 women of age 40-49 will die in annual SM as a result of radiation-induced breast cancer . It would be, however, more appropriate to express benefits and harms using the same effect measures.
It is particularly important to contrast net benefits and net risks in patients with and without SM. Of crucial importance for any prospective woman contemplating undergoing SM is to understand what outcome she can expect with and without SM. If individualized recommendations called by Qaasem et al is to become reality , estimates of net benefits and net harms of SM in women with different baseline risks of dying from breast cancer without undergoing SM should have been included in the recent ACP guidelines/systematic review. Had the authors presented data in such a way, they may have calculated that in the BEST case scenario for women at "average risk" of developing breast cancer, SM may save 46 lives/100,000 women screened over 10 years, at the cost of 30/100,000 lives lost. In the WORST case scenario, net benefits is actually negative, and more lives will be lost than saved [see below].
We believe that presenting data in this way may better help women understand benefits and harms of SM which need to be contrasted against their own individual risk for development of breast cancer. Only in this way can we truly exercise a women's preferences and values and preserve their autonomy consistent with ethical and rational decision-making .
Calculation of net benefits  (outcome: breast cancer deaths):
Net Benefits (B)= BC "“ BC*(1-RRR) "“ H
BC= Mortality from breast cancer without SM; RRR= relative reduction in breast cancer mortality due to SM; H= radiation-induced breast cancer deaths
Net harms (H) = Mortality without breast cancer- breast cancer mortality due to SM= 1-(1-H)= H
BEST CASE SCENARIO:
BC= 3.3/1,000 women (average risk) RRR=23%  H=30/100,000 women 
B= 0.0033 -0.0033*(1-0.23)-0.00030 = 0.00046 (= 46/100,000 lives saved) H=0.00030 (30/100,000 lives lost) B/H=1.5 (If woman's preferences are not taken into account, this B/H ratio translates into benefits of SM outweighing its harms only when probability of breast cancer exceeds 39.5%.)
WORST CASE SCENARIO
B= 0.0033 -0.0033*(1-0.07)-0.00030 = -0.000069 (negative net benefits; 69 lives lost/1,000,000 screened)
H= 200/100,000 women1
B= 0.0033 -0.0033*(1-0.07)-0.0020= -0.001769 (negative net benefits; 1769 lives lost/1,000,000 screened)
1. Armstrong K, Moye E, Williams S, Berlin JA, Reynolds EE. Screening Mammography in Women 40 to 49 Years of Age: A Systematic Review for the American College of Physicians. Ann Intern Med 2007;146(7):516-526.
2. Qaseem A, Snow V, Sherif K, et al. Screening Mammography for Women 40 to 49 Years of Age: A Clinical Practice Guideline from the American College of Physicians. Ann Intern Med 2007;146(7):511-515.
3. Djulbegovic B, Lyman G. Screening mammography at 40-49 years: regret or regret? Lancet 2006;368:2035-2037.
4. Djulbegovic B, Hozo I, Lyman G. Linking evidence-based medicine therapeutic summary measures to clinical decision analysis. MedGenMed 2000(January 13):http://www.medscape.com/Medscape/GeneralMedicine/journal/2000/v02.n01/mgm0113.djul/mgm0113.djul -01.html.
5. Moss SM, Cuckle H, Evans A, L. J, Waller M, Bobrow L. Effect of mammographic screening from age 40 years on breast cancer mortality at 10 year's follow-up: a randomised controlled trial. Lancet 2006;368:2053-60.
Armstrong K, Moye E, Williams S, Berlin JA, Reynolds EE. Screening Mammography in Women 40 to 49 Years of Age: A Systematic Review for the American College of Physicians. Ann Intern Med. 2007;146:516-526. doi: 10.7326/0003-4819-146-7-200704030-00008
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Published: Ann Intern Med. 2007;146(7):516-526.
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