Breast screen treatment concerns

Women aged 50 to 70 are invited for screening in the UK

Breast screening could lead to 10% of those checked having unnecessary treatment, a study has suggested.

Swedish researchers looked at some 42,000 women in a breast screening trial from 1976 to 1986.

The scientists, writing in the British Medical Journal, accept screening can reduce deaths, but say "over-diagnosis" is a problem.

But a spokeswoman for the NHS screening programme said the benefits outweighed the risks.

It is finally time to accept that, although breast screening by mammography is far from perfect, it is worthwhile

BMJ editorial

Over-diagnosis is defined as cases of cancer that would never have come to the attention of doctors during a woman's lifetime if it were not for screening.

This can result in invasive treatment such as surgery and radiotherapy which might never have been necessary had the woman had not attended for breast screening.

'More balance'

The researchers from Malmo University Hospital used data from a breast cancer screening trial on 42,283, women aged 55 to 69, carried out in Sweden between 1976 and 1986.

Half the women were screened, while the rest were not.

The women were then followed until December 2001, to see which developed breast cancer.

Looking at the numbers diagnosed, the researchers estimated that the rate of over-diagnosis of breast cancer was 10% in women who were screened, compared with those who were not.

Earlier studies looking at the problem of over-diagnosis had revealed rates of up to 54% but a more recent study had put it much lower at 1%, the researchers said.

They suggested that these previous studies, unlike their research, were not based on direct observations.

Dr Sophia Zackrisson, who led the study, said: "It is widely agreed that screening using mammography can reduce mortality in breast cancer.

"The rate of over-diagnosis is another issue to be considered in the ongoing discussion about clinical and public health implications of breast cancer screening."

Debate 'over'

In a second paper in the BMJ, researchers from the Nordic Cochrane Centre in Copenhagen said women should be given more information about the benefits and risks of breast screening.

Advocates say the benefits of detecting cancer outweigh the risks of screening

They looked at mammography invitations from English-speaking countries, including the UK, and Scandinavian countries which operated screening programmes.

They found 97% mentioned the main benefit of screening - a reduction in breast cancer mortality - but none mentioned the risk of over-diagnosis and subsequent over-treatment.

They wrote: "We believe that the information included with invitations should be more balanced, using absolute numbers to describe the likelihood of benefits and harms, and applying to the same time span if possible."

Consumer groups should be involved in putting the information together, they suggested.

Last week a report revealed that the NHS breast screening programme saves more than 1,000 lives in England each year.

The programme, which began in 1988, saves the lives of 1,400 women every 12 months and lessens the chance of patients having to be treated with a mastectomy, the study said.

And an editorial in the BMJ says it is now time to end the debate over whether screening is worthwhile.

"It is finally time to accept that, although breast screening by mammography is far from perfect, it is worthwhile," it says.

And Julietta Patnick, director of the NHS Cancer Screening Programmes said: "For lives to be saved breast screening must detect cancers in the early stages.

"While a small number of women may not benefit from early treatment, a report published last week shows that the benefits of breast screening far outweigh the risks.

"I would strongly encourage all women to make an informed choice to attend for screening when invited."