A major review of breast cancer screening services in Europe, jointly led by researchers at Queen Mary, University of London, has concluded that the benefits of screening in terms of lives saved outweigh the harms caused by over-diagnosis.
The results, which are published in a special supplement of The Journal of Medical Screening September 13, show that for every 1,000 women screened every two years from the age of 50 to the age of about 68-69, between seven and nine lives would be saved, and four cases would be over-diagnosed.
The European Screening Network (EUROSCREEN) working group, with members from nine European countries where outcome of screening programmes have been assessed, reviewed the estimates of benefit in published European studies in terms of breast cancer deaths prevented, and the major harms, in particular, the rates of what are called "over-diagnosed" cancers. These are breast cancers diagnosed as a result of screening, which would never have given rise to any symptoms during a woman's lifetime and would not have been diagnosed had she not been screened.
A second working group -- European Network for Indicators on Cancer (EUNICE) -- reviewed the organisation, participation rates and main performance parameters of 26 screening programmes in 18 countries, involving 12 million women, between 2001 and 2007. The reports from both working groups have contributed to the review just published.
Stephen Duffy, Professor of Cancer Screening at the Wolfson Institute of Preventive Medicine at Barts and The London School of Medicine & Dentistry, part of Queen Mary, University of London (UK), who is one of the coordinators of the EUROSCREEN working group and co-author of the supplement, said: "This is the only comprehensive review of the results of breast screening services in Europe. It reports results from screening millions of women, and confirms that the screening services are delivering the benefits expected from the research studies conducted years ago. In particular, it is good news that lives saved by screening outweigh over-diagnosed cases by a factor of two to one."
The researchers also found that for every 1,000 women screened, 170 women would have at least one recall followed by a non-invasive assessment before absence of cancer could be confirmed (a negative result), and 30 women would have at least one recall followed by invasive procedures, such as a biopsy, before confirming a negative result. Screening results that lead to recalls in these circumstances are called "false positives" and can cause women stress and anxiety until the negative result is confirmed.
Dr Eugenio Paci, Director of the Cancer Prevention and Research Institute in Florence, Italy, who is a second EUROSCREEN coordinator and co-author, said: "By weighing up the pros and cons of breast cancer screening programmes we hope to ensure that women are fully aware of the chief benefits and harms and can make a fully informed choice when they decide whether or not they wish to attend screening. There has been quite a lot of discussion recently over the worth of breast cancer screening and for this reason it is timely that the international group of experts has assessed the impact of population-based screening in Europe and has found that it is contributing to the reduction in deaths from the disease.
"We believe that not only should our conclusions be communicated to women offered breast screening in Europe, but that, in addition, communication methods should be improved in order to raise women's awareness, and to make information more accessible, relevant and comprehensible."
Breast cancer facts and figures:
- Worldwide, breast cancer is the most frequent cancer among women and approximately 1.38 million women were diagnosed with this disease in 2008 (the year for which most recent figures are available).
- In Europe, including non-European Union (EU) countries, 425,000 new cases of breast cancer were diagnosed in 2008 and 129,000 European women died of the disease. Data source: Ferlay J et al. GLOBOCAN 2008, Cancer Incidence and Mortality Worldwide. International Agency for Research on Cancer, 2010.
- In the UK breast cancer is the most common cancer among women, with more than 48,400 women diagnosed each year and around 11,550 women dying from the disease. The lifetime risk of being diagnosed with breast cancer is one in eight.
- The UK's NHS breast screening programme detected almost 16,500 cases of breast cancer in 2009/2010. Data source: Cancer Research UK key facts.
- In Europe, approximately 100,000-140,000 cancers are detected by screening each year among women aged 50-69.
- The UK is conducting a review of breast cancer screening in order to assess benefits and harms, chaired by Professor Sir Michael Marmot, and to which Prof Duffy submitted evidence earlier this year.
- EUROSCREEN working group. Summary of the evidence of breast cancer screening outcomes in Europe and first estimate of the benefit and harm balance sheet. Journal of Medical Screening, 2012, volume 19, supplement 1
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