Breast screening advice updated amid controversy over harms
30 October 2012 Last updated at 18:40 GMT
An independent review into breast cancer screening has warned that thousands of women are receiving treatment for the disease - including surgery - even though they may never have become seriously ill.
Researchers say that screening saves more than 1000 lives every year.
However, they found that three times as many women were given unnecessary treatment.
The BBC's health correspondent Branwen Jeffeys reports.