LONDON — Breast-cancer screening for women older than 50 saves lives, an independent panel in Britain has concluded, confirming findings in the United States and other studies.

However, the review found that for every life saved, roughly three other women were overdiagnosed, meaning they were unnecessarily treated for a cancer that would never have threatened their lives.

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

In Britain, mammograms are usually offered to women aged 50 to 70 every three years as part of the state-funded breast cancer screening program. Scientists said the British program saves about 1,300 women every year from dying of breast cancer while about 4,000 women are overdiagnosed. By that term, experts mean women treated for cancers that grow too slowly to ever put their lives at risk. This is different from another screening problem: false alarms, which occur when suspicious mammograms lead to biopsies and follow-up tests to rule out cancers that were not present. The study did not look at the false alarm rate.