A study that was conducted on about 80,000 women has noted that breast cancer screening does more good than harm, with any over-treatment justified by the number of lives saved.

Dangerous tumors can be spotted by mammograms but it also finds out lumps that are actually not dangerous exposing some women to undue anxiety and surgery.

Every three years across the UK women aged 50 to 70 are invited for NHS breast screening.

From 2012 in UK, screening will be extended to women who are 47 to 73 years old.

A data from 80,000 women from the age of 50, was focused on by experts from the Wolfson Institute of Preventive Medicine at Barts and the London School of Medicine and Dentistry. They looked at data from Sweden and England before and after the introduction of screening.

The research estimated that over a 20-year period in England about 5.7 breast cancer deaths were prevented for every 1,000 women screened.

About 2.5 lives were saved and one case was over-diagnosed for every 28 cases diagnosed.

Richard Winder, deputy director of NHS cancer screening programmes, said, "There is a risk of over-diagnosis, and possible subsequent over-treatment, associated with any screening programme.”