This study offers further evidence as to the substantial potential benefit of breast screening

Dr Peter Sasieni, Cancer Research UK

UK experts welcomed the extra evidence in support of breast screening.

The Swedish study updates the overview of four Swedish trials up to and including 1996, which covered women aged from their late 30s to their early 70s.

They looked at deaths from breast cancer in over 1,000 women, and found there was a 21% reduced mortality risk in women who had been screened.

The biggest reductions in death rate were in women aged 55 and over.

Dr Lennarth Nystrom, who led the study, said: "The advantageous effect of breast screening on breast cancer mortality persists after long-term follow-up.

"The recent criticism against the Swedish randomised controlled trials is misleading and scientifically unfounded."

Controversy

Writing in The Lancet, Karen Gelmon from the British Columbia Cancer Agency in Vancouver, Canada, said: "The data confirm that screening mammography has a real but modest effect to decrease mortality from breast cancer and that this effect varies with age."

She added that women who are otherwise well, especially those aged between 55 and 69, and who are concerned about breast cancer, should be encouraged to attend screening - but warned less than half such women accessed the service in many western countries, partly because of the controversy around mammography.

But she added: "As breast cancer accounts for only about 4% of all deaths annually, even a 21% reduction in breast cancer mortality is barely measurable when all-cause mortality is the endpoint."

Dr Peter Sasieni of Cancer Research UK welcomed the Lancet research, saying it provided "additional evidence as to the effectiveness of mammography in the reduction of breast cancer mortality."

He added: "This study offers further evidence as to the substantial potential benefit of breast screening.

"It is now time to move on from arguing about the randomised trials and to concentrate on evaluating service screening to make sure it lives up to its potential."

Treatment challenge

Julietta Patnick, national co-ordinator of the NHS Cancer Screening Programmes, said: "While the full benefits of the NHS Breast Screening Programme will not be evident until the end of the decade, this paper corroborates our premise that breast screening saves lives, especially for women who accept their regular invitations.

"Sixty per cent of screen-detected cancers are in women returning to us for repeat screening.

"We know that breast screening works and encourage women to accept their invitation for screening. Of course, the ultimate challenge for all of us is to make sure that the cancers we detect are treated successfully."

In the UK, women are invited for mammograms between the ages of 50-64. By 2004, the programme will be extended to include women up to 70.

In 1999 to 2000, the NHS Breast Screening Programme detected 9,525 cancers - 6.39 per 1,000 screened - and 4,041 invasive cancers smaller than 15mm, which experts say are usually impossible to feel with the human hand.