Routine breast screening is beneficial, but it can often 'overdiagnose' benign lumps which will not cause any harm, according to a new UK review.

An independent UK panel of experts has found that routine breast cancer screening leads to a reduced risk of breast cancer death compared to if no screening takes place, but that screening can also result in overdiagnosis.

The experts say when breast cancer is detected by screening, it usually allows for earlier treatment and an improved outcome for the patient.

"However, concerns have recently been raised about overdiagnosis - where screening identifies a tumour, which is consequently treated by surgery, and often radiotherapy and medication, but which would have remained undetected for the rest of the woman's life without causing illness if it had not been detected by screening."

The expert panel, led by Professor Sir Michael Marmot, Director of the Institute of Health Equity at University College, London, UK, was set up to provide an independent review of the evidence for the pros and cons  of breast screening .

They analysed of 11 studies assessing whether breast cancer screening results in fewer deaths due to the disease, compared to when no screening takes place.

The results showed that women who are invited to breast cancer screening have a relative risk of dying from breast cancer that is 20% less than those who don't get routine screening.

The experts said for the approximately 307,000 women aged 50-52 years who are invited to begin screening every year, just over 1% will have an overdiagnosed cancer in the next 20 years.

The panel estimated that that for 10,000 UK women invited to screening from age 50 for 20 years, about 681 cancers will be found, of which 129 could be classified as 'overdiagnosis, and 43 deaths from breast cancer will be prevented.

However, the panel said further research will be needed to more accurately assess the benefits and harms of breast screening.

The research is published in The Lancet.