Breast screens 'do not directly cut cancer'
A study in the British Medical Journal compared countries with similar populations but which introduced screening at different times.
They found that all nations saw similar reductions in deaths from breast cancer - even though some introduced screening programmes up to 15 years later than others.
The researchers, from the UK, France and Norway, said that better treatment and improved health systems were more likely to have reduced death rates than screening programmes.
The Scottish Government and campaigners yesterday said screening still played a vital role in making sure women were diagnosed and treated early.
In Scotland, women are invited for mammography - special X-rays on the breasts - every three years between the ages of 50 and 70.
Figures show that in 2009/10, 75 per cent of women in Scotland attended for screening after being invited and almost 1,400 cancers were detected.
The research in the BMJ, led by the International Prevention Research Institute in Lyon, looked at mortality rates from breast cancer in three pairs of countries.
Sweden's screening programme reached national coverage 12 years before neighbouring Norway. But while Sweden's breast cancer death rate dropped 16 per cent between 1989 and 2006, Norway's fell by 24.1 per cent.
The Netherlands started screening in 1997, while nearby Belgium did not reach coverage close to 60 per cent until 2005.
Participation in screening in the Flanders region was low until about 2002-3, and by 2004-6 it was still below the coverage in the Netherlands.
But despite these differen-ces, there was a similar drop in deaths - by 25 per cent in the Netherlands, 20 per cent in Belgium and 25 per cent in Flanders.
In Northern Ireland, where screening started in the early 1990s, deaths fell by 29 per cent, while in the Republic of Ireland, where screening did not start to roll out until 2000, deaths were down 26 per cent.The researchers concluded: "Countries of each pair had similar healthcare services and prevalence of risk factors for breast cancer mortality but differing implementation of mammography screening, with a gap of about 10 to 15 years.
"The contrast between the time differences in implementation of mammography screening and the similarity in reductions in mortality between the country pairs suggest that screening did not play a direct part in the reductions in breast cancer mortality."
Audrey Birt, director for Scotland at Breakthrough Breast Cancer, said: "Detecting breast cancer early is crucial and screening helps us to do this.
"It's a combination of early diagnosis and improved treatments that really makes the difference."
She added: "Screening and treatments must go hand in hand if we are to succeed in the fight against breast cancer and we urge all eligible women to attend their screening appointments."
A Scottish Government spokeswoman said: "As with all cancers, the earlier a diagnosis is made, the better the chance of survival.
"Here in Scotland, screening of women aged 50 to 70 helps to detect nearly 1,500 breast cancers a year, with earlier detection helping to ensure earlier treatment and a better chance of survival
"While there is no doubt that improvements in treatment have helped contribute to rising survival rates, we cannot underestimate the importance of breast screening for women in Scotland."