Screening for Breast Cancer 'May Harm Women'

by Nic Fleming

Breast cancer screening may be doing more harm than good, a new report says today.

The research found that for every 2,000 women invited to have mammograms, one would have their life prolonged but 10 would endure potentially devastating and unnecessary treatment.

It suggested that most women having surgery, including mastectomies, radiotherapy and chemotherapy, following screening do so even though abnormalities identified in their cells would not have become a problem during their lifetime.

The research, a major review of studies covering half a million women, is published by the internationally-respected Cochrane Library.

Prof Michael Baum, a pioneer of England's £75 million-a-year screening programme, called for the National Institute for Health and Clinical Excellence to investigate whether it should continue.

Prof. Baum, Professor Emeritus of Surgery and visiting Professor of Medical Humanities at University College London, told The Daily Telegraph: "Up until now, my position has been that women should make an informed choice based on the facts of benefits to one women in 1,000 over 10 years on the one hand and the risks of over-diagnosis and false positives on the other. This latest evidence shifts the balance even further towards harm and away from benefits. If this report stands up, the NHS screening programme should be referred to the National Institute for Health and Clinical Excellence (NICE) to decide whether it should be closed down."

Dr Peter Gøzsche, an expert in internal medicine and director of the Nordic Cochrane Centre, who led the new research, said many women were being treated for slow-growing cancers that might never have affected them if they were not picked up during screening.

Dr Gøzsche said: "Information given to women when they are invited for screening and that they can get on the internet is considerably biased in that it underlines the benefits and usually completely omits major harms such as over-diagnosis. If I were a 50-year-old woman and I was called for screening, I would decline because I think the risk is so big for harm that I wouldn't participate in this lottery. But others have another opinion and that is fine as long as they get balanced information. I know many female doctors who have chosen not to get screened because they are aware of the data we publish in the Cochrane Library. There are also female doctors who wish to be screened. It's an individual decision."

One in nine women in the UK is diagnosed with breast cancer at some time. There were 41,000 cases in 2004 - up 81 per cent since 1971.

Dr Gøzsche and colleagues identified the seven best trials investigating both the benefits and negative outcomes associated with screening. They found women invited to be screened have a 15 per cent lower risk of death from breast cancer compared with those not invited.

The absolute reduction in the risk of dying from breast cancer as a result of screening was 0.05 per cent. The increased chance of a woman called for screening being diagnosed and then treated unnecessarily for a slow-growing or benign cancer was 30 per cent - an absolute risk increase of 0.5 per cent. On top of the 10 in every 2,000 given unnecessary treatment, they found a further 200 would experience weeks or months of anxiety because of "false positive" findings - the discovery of cell changes that later turned out to be benign.

About a fifth of breast cancers detected during screening are early cancers known as ductal carcinoma in situ (DCIS). Most women with DCIS have mastectomies even though doctors do not know whether they will spread.

Julietta Patnick, director of NHS Cancer Screening Programmes, said: "The trials in any review like this will be based on what has gone on in the past, not what is going on now. Equipment and expertise have moved on. Over-diagnosis is a fact, but we estimate that for every 2,000 women screened over 10 years, we probably diagnose five who would otherwise not present but we will also save five lives."
The Daily Telegraph, 18th October 2006