Image caption To screen or not to screen? Mammograms reduce the risk of dying from breast cancer

Breast cancer screening saves the lives of two women for every one patient who receives unnecessary treatment, according to a major European review.

There has been a fierce debate about the use of screening, and policy is being reviewed in England.

The latest study, published in the Journal of Medical Screening, said at least seven lives were saved for every 1,000 women screened.

Health charities say the findings will provide further clarity for women.

Mammograms spot dangerous tumours, increasing the chances of survival, but also detect lumps that are essentially harmless, exposing some women to undue anxiety and surgery.

Screening doesn't just save lives today or tomorrow, it saves lives 10-20 years down the line Prof Stephen Duffy , Queen Mary, University of London

Tens of thousands of women die from breast cancer across Europe each year. The effectiveness of screening programmes across the continent was evaluated in a series of studies.

It concluded that for every 1,000 women screened, between seven and nine lives were saved and four cases were over-diagnosed.

One of the lead researchers Prof Stephen Duffy, from Queen Mary, University of London, said the study "confirms that the screening services are delivering the benefits expected from the research studies conducted years ago".

"In particular, it is good news that lives saved by screening outweigh over-diagnosed cases by a factor of two to one," he said.

"Screening doesn't just save lives today or tomorrow, it saves lives 10-20 years down the line."

In England, the Department of Health is reviewing the evidence around breast cancer screening, which started in 1988. The findings will be published later this year.

Breast screening: The UK debate 1988: UK women over the age of 50 first offered screening every three years

2002: World Health Organization estimates screening reduces deaths by about a third

Jan 2011: Review of large clinical trials says for every 2,000 women screened, one life is saved, 10 women have treatment they don't need and 200 face the stress of false positive results

Oct 2011: Government cancer expert announces review of evidence

Oct 2011: Department of Health says its advice is unchanged and urges all women to go to screening when invited

The charities Breakthrough Breast Cancer and Breast Cancer Campaign said in a joint statement: "This hugely detailed, impressive piece of work supports the widely held view that breast screening saves lives by helping to detect breast cancer early.

"As charities, we will be working closely with the screening programme to ensure women receive the best possible information on both the potential benefits and risks of breast screening.

"In the meantime, if women have any questions we advise them to discuss these with their doctor."

Dr Julie Sharp, Cancer Research UK's senior science information manager, said: "This study adds to the information which is currently being independently reviewed on the harms and benefits of breast screening. The independent panel is taking account of all relevant views, studies and evidence. We look forward to the conclusions, which will be available later this year."