Breast cancer Screening

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Breast cancerScreening
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NHS Breast Screening ProgrammeNHSBSP Publication
No. 61. Feb 2006www.cancerscreening.nhs.uk

• NHS Breast Screening Programme (NHSBSP) began in
  1988
• Aims to invite all women aged 50-70 years once
  every 3 years
• Number of breast cancer registrations has
  increased by almost 50 since NHSBSP began
• Cancers detected by screening are smaller and
  mastectomy is less likely
• NHSBSP plus earlier symptomatic presentation and
  greater use of adjuvant therapy has reduced
  mortality from breast cancer
• Mammography screening trials show a 25 relative
  risk reduction in mortality (ITT), equates to 35
  in women regularly screened
• NHSBSP saves an estimated 1400 lives each year in
  England.

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Benefits vs. harms of screeningNHSBSP
Publication No. 61. Feb 2006

• About 1 in 400 women regularly screened over a 10
  year period will be prevented from dying from
  breast cancer
• About 1 in 8 women regularly screened will be
  recalled for further tests over a 10-year period
• Breast cancer will be diagnosed in only a few of
  these
• Delicate balance between reducing recall rates so
  far that small cancers are missed and calling
  back too many women causing anxiety and possibly
  reducing re-attendance
• Among women routinely screened and diagnosed with
  breast cancer
• 1 in 8 fewer women will die than would have done
  if theyd not been screened
• 1 in 8 spared mastectomy
• 1 in 8 women have a cancer detected (and treated)
  which would not have affected her had she not
  been screened.

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NHSBSP Publication No. 61. Feb 2006
Positive predictive value (PPV) of abnormal
mammogram 19 i.e. 19 of people with abnormal
mammogram have breast cancer
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Overdiagnosis in breast cancer screening
(1)Jorgensen KJ, Gøtzsche PC. BMJ
2009339b2587Welch HG. BMJ 2009339b1425
MeReC Rapid Review Blog No. 417
The absolute risks and benefits of breast cancer
screening, including the level of overdiagnosis,
should be communicated to women in a balanced way
so they can make an informed decision to have
screening or not.

• From meta-analysis, the total overdiagnosis of
  breast cancer in publicly available mammography
  screening programmes was estimated as 52 (95CI
  46 to 58)
• i.e. about one in three cancers is overdiagnosed
• For every 1000 women (gt50 years) who are screened
  for breast cancer annually for 10 years
• 1 woman will avoid dying from breast cancer
• 2 to 10 women will be overdiagnosed and treated
  needlessly
• 10 to 15 women will be told they have breast
  cancer earlier than they would otherwise have
  been told, but this will not affect their
  prognosis
• 100 to 500 women will have at least one false
  alarm (approximately half these women will
  undergo a biopsy).

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Overdiagnosis in breast cancer screening
(2)Welch HG. BMJ 2009339b1425

• Mammography is one of medicines close calls
  a delicate balance between benefits and harms
  where different people in the same situation
  might reasonably make different choices.
• Mammography undoubtedly helps some women but
  hurts others. No right answer exists, instead it
  is a personal choice.

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Summary

• Breast cancer screening contributes to the
  falling mortality from the disease
• About 1 in 400 women regularly screened over a
  10-year period will be prevented from dying from
  breast cancer
• 1 in 8 women diagnosed with breast cancer avoids
  a mastectomy she would have needed, had she not
  had the cancer diagnosed by screening
• The benefits must be weighed against the harms
• About 1 in 8 women regularly screened will be
  recalled for further assessment over a 10-year
  period, but very few of these have the disease
• 1 in 8 women screened and diagnosed have a cancer
  which would not have affected her had she not
  been screened.