Breast cancer screening

Current situation

  • Mammography is currently offered to all women aged 50–70 years in the UK.
  • Mammography is about 90 per cent sensitive in women over 50 years and probably even less sensitive in women receiving HRT.
  • Over-diagnosis of breast cancer is the detection of cases that would have never come to clinical attention without screening.
  • For every 1,000 women screened over 10 years, between 167 and 251 receive an abnormal result (BMJ 2005; 330: 936–40).
  • The incidence of breast cancer has increased by 16 per cent since 2004. This is mainly due to better detection at an earlier stage (Ann Onc 2007; 18: 581–92).

What is the evidence?

  • A 20-year follow-up study found that screening with mammography reduces mortality from breast cancer by
    23 per cent (Lancet 2003; 361: 1,405).
  • Screening can lead to over-diagnosis and over-treatment (J Med Screen 2005; 12: 128–33).
  • Even during subsequent screening, the incidence of breast cancer is around 30 per cent higher than before screening (Eur J Cancer Prev 2005; 14: 117–28).
  • The rate of over-diagnosis of breast cancer in women aged 55–69 years has recently been shown to be 10 per cent (BMJ 2006; 332: 689–91).
  • Women are being given insufficient information about the possible harmful consequences of breast cancer screening (BMJ 2004; 328: 148).
  • The latest Cochrane review said that breast cancer screening saves lives, specifically by reducing breast cancer mortality (Cochrane Database Syst Rev 2006; 18 Oct: CD001877). 
    But the review concluded it is still not clear whether screening does more good than harm.
  • Breast screening of women aged under 50 years does not appear to have a significant impact on cancer deaths, according to a recent study (Lancet 2006; 368: 2,053–60).

Implications for practice

  • Screening 250 women has been calculated to prevent about one death from breast cancer (BMJ 2006; 332: 691).
  • Overdetection of breast cancer may cause harm through unnecessary labelling and treatment of patients as having a cancer that, without screening, might never have presented.
  • MRI is being introduced to screen women with high-risk mutations in the genes associated with breast cancer.

Available guidelines

  • An Information Centre for Health and Social Care report showed the number of breast cancers detected by screening has risen by 62 per cent since 2001.
    At the same time, the number of women dying from breast cancer has fallen (http://www.ic.nhs.uk/pubs/bsp 0506).

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