One million women each year will develop breast cancer worldwide and many trials have looked at whether screening has an impact on outcome in terms of mortality and morbidity. Several countries have now set up screening programmes to call women for routine screening.
The programme was initiated in 1988 following the Forrest Report. There are 80 units across the UK, each responsible for the screening of approximately 45,000 women. The budget for the screening is around £96 million per year.
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The breast cancer screening programme in the UK has been set up to allow for the early detection and treatment of breast cancer in women.
- The Canadian Task Force found that mammography is associated with significant reductions in the relative risk of death from breast cancer in the 50-69 years age group. The benefits of mammography for women aged 60-69 years (number needed to screen (NNS) 432) are greater than for women aged 50-59 years (NNS 910). Screening about 720 women aged 50-69 years once every 2-3 years for about 11 years would prevent one death from breast cancer, but it would also result in about 204 women having a false-positive result on a mammogram and 26 women having an unnecessary biopsy of their breast.
- For women aged 40-49 there is only limited evidence of a reduction in mortality. This may be due to the difficulties in interpreting mammograms in premenopausal women, due to glandular breast tissue, and also to the lower incidence of breast cancer in this age group.
- Research has shown that between 2 and 2.5 lives are saved in England for every overdiagnosed case.
- Beral and Peto have written that 'In the UK, breast cancers are diagnosed earlier and treated more effectively than they were in the 1980s, and breast cancer mortality in middle age has been falling steeply, more so than in any other major European country.'
- A Cochrane review concluded that screening is likely to reduce breast cancer mortality. However, as the effect was lowest in the adequately randomised trials, a reasonable estimate is a 15% reduction corresponding to an absolute risk reduction of 0.05%. This needs to be balanced against risks of over-diagnosis - see below.
- There is some evidence to suggest that reduction in mortality is independent of screening practice.
All women between the ages of 50 and 70 are invited to attend for screening every three years. It is a rolling programme, which means that not all women will be invited when they reach 50 years, but all will be invited before their 53rd birthday. Women over the target age may request mammography through their GP. The programme is now phasing in an extension of the age range of women eligible for breast screening to those aged 47 to 73. This started in 2010 and is expected to be complete by 2016.
In England 77.2% of women aged 53-70, who were eligible for screening, had a result recorded within the last 3 years. The rate is lower (68.9%) in London where the population can be hard to reach because of its diversity and transient nature.
- 2.3 million women aged 50-70 were invited for screening.
- 14,725 cases of cancer were diagnosed in women of all ages screened.
- This is an average detection rate of 7.2 cancers per 1,000 women screened.
Women who have a family history of breast cancer can access advice about their risks and further screening if required, through their GP.
Otherwise, primary care clinicians should be aware of women who may be at higher risk of breast cancer - for example, not breast-feeding long-term, having no children or few children, having children at late ages (especially over 30), obesity (for postmenopausal women only), diethylstilboestrol exposure in utero and high consumption of alcohol - and advise them opportunistically of breast awareness.
What screening involves
Screening in the UK is a nationally co-ordinated programme, with national standards monitored through a quality assurance network.
Screening takes place in the form of clinical examination and mammography. This allows small tumours to be detected before they are palpable. Since 2003, two images of each breast have been taken, craniocaudial, and mediolateral, and this increases the detection rate of even smaller abnormalities by up to 43%. Other assessment centres may use ultrasound of the breast.
23% of women having a mammogram are called back; some of these are for technical reasons, but 4.4% require further assessment. 42% of these women have either fine-needle aspiration or core biopsy. For 2009-2010, of 74,289 women who had a positive mammogram only 19% actually had breast cancer.
Negative effects of screening
Recent papers have highlighted that screening may lead to over-diagnosis and over-treatment. A Cochrane review (whilst agreeing that screening did lower breast cancer mortality) declared that screening also led to 30% over-diagnosis and over-treatment, or an absolute risk increase of 0.5%. This meant that for every 2,000 women invited for screening throughout 10 years, one will have her life prolonged and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. There may be evidence to support an overall net harm for women screened.
The process is a very anxious time for women but research suggests that women are able to balance the anxiety against the effectiveness.
Further reading & references
- Quality Assurance Guidelines for Surgeons in Breast Cancer Screening, NHS Cancer Screening Programmes, NHSBSP Publication No 20, Fourth edition (March 2009}
- Primary breast cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up; European Society for Medical Oncology (2011)
- Cancer UK
- Forrest APM; Breast Cancer Screening: report to the health ministers for England, Wales, Scotland and Northern Ireland, HMSO, 1986
- NHS Breast screening programme
- Tonelli M, Gorber SC, Joffres M, et al; Recommendations on screening for breast cancer in average-risk women aged 40-74 CMAJ. 2011 Nov 22;183(17):1991-2001.
- Duffy SW et al. Absolute numbers of lives saved and overdiagnosis in breast cancer screening, from a randomized trial and from the Breast Screening Programme in England. Journal of Medical Screening. 2010.
- Beral V, Peto R; UK cancer survival statistics. BMJ. 2010 Aug 11;341:c4112. doi: 10.1136/bmj.c4112.
- Gotzsche PC, Nielsen M; Screening for breast cancer with mammography. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD001877.
- Autier P, Boniol M, Gavin A, et al; Breast cancer mortality in neighbouring European countries with different levels BMJ. 2011 Jul 28;343:d4411. doi: 10.1136/bmj.d4411.
- Breast screening, Prodigy (December 2011)
- Raftery J, Chorozoglou M; Possible net harms of breast cancer screening: updated modelling of Forrest BMJ. 2011 Dec 8;343:d7627. doi: 10.1136/bmj.d7627.
- Yasunaga H, Ide H, Imamura T, et al; Women's Anxieties Caused by False Positives in Mammography Screening: A Contingent Valuation Survey.; Breast Cancer Res Treat. 2006 Jul 4;.
|Original Author: Dr Hayley Willacy||Current Version: Dr Hayley Willacy||Peer Reviewer: Prof Cathy Jackson|
|Last Checked: 13/06/2012||Document ID: 1367 Version: 24||© EMIS|
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