Breast cancer screening leads to unnecessary treatmentDebate on mammography screening continues
Up to a quarter of breast cancer cases detected by routine screening would not have caused women symptoms or illness during their life, according to new research.
A study of breast cancer screening in Norway estimated that between 15 and 25 per cent of breast cancer cases are "over-diagnosed", leading to unnecessary treatment such as radiotherapy, chemotherapy and even surgery.
Study author Dr Mette Kalager, a visiting scientist at Harvard School of Public Health and a researcher at the Telemark Hospital in Norway, said : "Mammography might not be appropriate for use in breast cancer screening because it cannot distinguish between progressive and non-progressive cancer.
"Radiologists have been trained to find even the smallest of tumours in a bid to detect as many cancers as possible to be able to cure breast cancer.
"However, the present study adds to the increasing body of evidence that this practice has caused a problem for women - diagnosis of breast cancer that wouldn't cause symptoms or death."
Breast cancer screening by mammography is a hotly debated topic among health experts worldwide, with some arguing that, because of the problems of over-diagnosis, it does more harm than good.
In the latest study, Harvard researchers analysed data on nearly 40,000 cases of breast cancer in Norwegian women. Because breast cancer screening was phased in at different times between 1996 and 2005, this allowed the researchers to compare breast cancer cases in women who had been offered screening with those who had not.
Among the 7,793 women diagnosed with breast cancer through the screening program, 15 to 25 per cent were over-diagnosed, the study found.
Based on these figures, the researchers estimated that for every 2,500 women screened, one death from breast cancer will be prevented, but six to 10 women will be over-diagnosed and treated unnecessarily.
Dr Kalager said the findings suggest that women should be well-informed not only about the potential benefits of mammography, but also about its possible harms - including mental distress, biopsies, surgeries, or chemotherapy and hormone treatments for a disease that would never have caused them symptoms.
Dr Caitlin Palframan, of the charity Breakthrough Breast Cancer, said: "The rate of over-diagnosis in breast cancer screening has been debated widely and led to confusing messages for women on the effectiveness of breast screening.
"However, we believe that screening is vital as it helps detect breast cancer early when treatment options are likely to be less aggressive and have more successful outcomes.
"The National Cancer Director has commissioned an independent review of all the evidence that underpins the NHS Breast Screening Programme and we expect this will soon provide clarity on this issue."
The study is published in the Annals of Internal Medicine.
This article was published on Tue 3 April 2012
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