LONDON (October 30, 2012)--A panel in Britain confirms the life-saving nature of breast cancer screening, but says it comes at a cost.

The panel’s review found that for every life saved, roughly three other women are over-diagnosed and unnecessarily treated for a cancer that would never have threatened their lives.

The expert panel commissioned by Cancer Research U.K. and Britain's department of health analyzed evidence from 11 trials in Canada, Sweden, the U.K. and the U.S.

Scientists say the British program saves about 1,300 women every year from dying of breast cancer while about 4,000 women are over-diagnosed.

The study did not look at the rate of false alarms from the screening.

Each year, more than 300,000 women aged 50 to 52 are offered a mammogram through the British program.

The review was published online Tuesday in the Lancet journal.