Journals Club - Breast cancer screening

Curriculum statement 10.1 women's health.

Key trials

  • Breast cancer screening can lead to overdiagnosis and over-treatment (J Med Screen 2005; 12: 128-33).
  • The rate of over-diagnosis of breast cancer in women aged 55-69 years is 10 per cent (BMJ 2006; 332: 689-92).
  • Breast screening of women aged under 50 years does not appear to have a significant impact on cancer deaths (Lancet 2006; 368: 2,053-60).
  • The major problem with screening is the unnecessary treatment of harmless lesions that would not have been identified without screening (BMJ 2009; 338: b86).
  • A systematic review has shown that a woman with a false-positive mammography result had higher levels of anxiety and stress even several months after receiving the result (Ann Intern Med 2007; 146: 502-10).
  • Reassuringly, there is some evidence to suggest that screening does not delay presentation of breast cancer symptoms to the GP (Int J Cancer 123; 3: 680-6).

Screening does reduce mortality

Evidence base

  • Although a Cochrane Review found breast cancer screening saves lives, specifically by reducing breast cancer mortality, it still concluded that it is not clear whether screening does more good than harm (Cochrane Database Syst Rev 2006; 18 Oct: CD001877).
  • The number of women whose life is prolonged by screening has been estimated to be five in every 2,000 women in a 10-year period (Screening for breast cancer in England: past and future. NHS Cancer Screening Programmes, 2006).
  • Clinical Knowledge Summaries clearly lists the benefits and harm of screening.

Guidelines

  • The NHS Breast Screening Programme in England began in 1988, and provides three-yearly breast screening for women 50-70 years.
  • Each woman undergoing breast screening is currently sent a leaflet: Breast Screening: The Facts. This is to be re-written to include more on the potential harm of screening.
  • The GMC states that 'you must tell patients if an investigation or treatment might result in a serious adverse outcome, even if the likelihood is very small' (Consent: patients and doctors making decisions together. GMC, 2008).

A new leaflet will state that:

  • If 2,000 women are screened regularly for 10 years, one will benefit, as she will avoid dying from breast cancer.
  • At the same time, 10 healthy women will, as a consequence, become cancer patients and will be treated unnecessarily (BMJ 2009; 338: b86).

Contributed by Dr Louise Newson, a GP in the West Midlands

Key learning points

  • Risks of breast cancer screening should not be underestimated.
  • Overdiagnosis and overtreatment needs to be discussed with women.
  • Psychological effects of false-positive tests can be long-lasting.
  • The NHS has agreed to re-write leaflets for women attending screening.

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