AS many as 4000 women a year are given unnecessary treatment for cancer through breast screening in the UK, an independent review has found.

But the investigation into the national breast screening programme said the benefits outweighed the harms, with the relative risk of dying from breast cancer 20% less than those who did not go through the clinical investigation.

The investigation panel estimated that for 10,000 women in the UK invited to screening from age 50, for 20 years, about 681 cancers would be found, of which 129 would represent over-diagnosis, and 43 deaths from breast cancer would be prevented.

Last week, Professor Peter Gotzsche claimed 10 women were harmed by unnecessary treatment for every woman saved.

But the panel concluded that while it estimated for every breast cancer death prevented there were three over-diagnosed cases, the UK breast screening programmes confer "significant benefit". It said: "On the positive side, screening confers a reduction in the risk of mortality from breast cancer. On the negative side, there is the knowledge that she has perhaps a 1% chance of having a cancer diagnosed and treated that would never have caused problems if she had not been screened."