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BMJ. 2007 April 14; 334(7597): 769.
PMCID: PMC1852008
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When should routine screening for breast cancer start?

While the benefits of routine screening for breast cancer seem to outweigh harms in women aged 50 years and older, this may not be so for women in their 40s. A systematic review of randomised trials and observational studies examined the evidence on benefits and risks of mammography screening for women aged 40-49.

Although a meta-analysis showed that screening in this age group reduced mortality from breast cancer by 7-23%, risks were considerable. The linked editorial (pp 529-31) simplifies the numbers—for every 10 000 women who have yearly routine mammography from age 40, only six women might benefit through reduced risk of dying of breast cancer. Most women will not have breast cancer, and some will have it detected too late for a cure.

On the other hand, after 10 routine mammograms, up to half of the women will have one false positive test result. This will usually be followed by further diagnostic procedures, and about 2000 women will undergo biopsy. Apart from associated anxiety and costs, other risks include exposure to radiation, overdiagnosis, and false reassurance. Linked clinical guidelines suggest that decisions on whether to screen women in their 40s need to be made individually (pp 511-5).


  • Ann Intern Med 2007;146:516-26
  • Ann Intern Med 2007;146:529-31
  • Ann Intern Med 2007;146:511-5

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