"Lives saved by screening outweigh over-diagnosed cases by two to one."
Experts have long debated whether breast cancer screening offers women genuine benefits, but now the first comprehensive review of screening programmes in Europe has concluded that the benefits outweigh the harm done by over-diagnosis. And this, say the scientists behind the review, is something that women who are offered a mammogram should be told.
Why has there been controversy over screening? Critics have pointed out that it can result in over-diagnosis of cancer, causing women unnecessary anxiety, testing, and even unnecessary treatment. In some cases women are treated for breast cancers found during screening which would not have caused them any symptoms during their lives. On the positive side supporters pointed out that screening catches cases of breast cancer and allows women to be treated earlier than would otherwise have happened.
The new conclusions are based on a major review of breast cancer screening services in Europe, which was jointly led by researchers at Queen Mary, University of London. The results have been published in a special supplement of The Journal of Medical Screening.
The results from the review show that for every 1,000 women screened every two years from the age of 50 to 68 or 69, seven to nine lives would be saved, compared to four cases being over-diagnosed. (Estimates put the number of lives saved by the NHS Breast Screening Programme at 1,400 each year.)
Stephen Duffy, Professor of Cancer Screening at the Wolfson Institute of Preventive Medicine at Barts and The London School of Medicine & Dentistry, a co-author of the report, 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.”
Co-author Dr Eugenio Paci, Director of the Cancer Prevention and Research Institute in Florence, Italy, 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.”
Breast cancer facts
*Breast cancer is the most common cancer among women around the world. Approximately 1.38 million women were diagnosed with this disease in 2008.
*Breast cancer is the most common cancer in women in the UK. More than 48,400 women are diagnosed with this disease each year. About 11,550 UK women die from breast cancer each year.
*A woman’s lifetime risk of being diagnosed with breast cancer is one in eight.
*The NHS breast screening programme detected almost 16,500 cases of breast cancer in 2009/10.
About the review
The European Screening Network (EUROSCREEN) working group, which has members in nine European countries where the outcome of screening programmes have been assessed, reviewed the estimates of benefits and harms in published European studies.
A second working group – European Network for Indicators on Cancer (EUNICE) - reviewed 26 screening programmes in 18 countries, between 2001 and 2007, involving 12 million women. This group studied the organisation, participation rates and main performance parameters of the programmes.