Mammography screening cuts breast cancer deaths by 40%

Study on women aged 50 to 69 years bolsters the case for national screening programmes

Women aged 50-69 years who attend mammography screening reduce their risk of dying from breast cancer by 40 per cent compared with women who are not screened, a major international review of the latest evidence on breast cancer screening has found.

The review, commissioned by the International Agency for Research in Cancer (IARC), the World Health Organisation’s specialised cancer agency, also concluded there were benefits in screening older women aged 70 to 74.

However there was limited evidence for the benefits of screening younger women in the 40 to 49 age group.

Published on Wednesday night in the New England Journal of Medicine, the findings by a group of 29 international experts help bolster the case for national breast screening programmes such as BreastCheck following the publication of some research in the last year which suggested screening may do more harm than good.


The IARC working group concluded there were some harms associated with the early detection of breast cancer using mammography screening. Concerning overdiagnosis, it acknowledged that mammography screening detects breast cancers that would never have been diagnosed or caused harm if the women had not been screened.

The risk of a false positive result has short-term negative psychological consequences, the experts said.

“Careful consideration of both the benefits and harms of mammography screening shows a net benefit from inviting women 50-69 years old”, Dr Marie-Beatrice Lauby-Secretan, an IARC scientist said.

“The significant reduction in breast cancer mortality observed in this age group outweighs the effects of overdiagnosis and other adverse effects.”

Overall, women who are invited to attend mammography screening have a 23 per cent risk reduction in breast cancer death (owing to some attending and some not), compared with women not invited by routine screening programmes.

In Ireland and the UK, this relative risk translates to around eight deaths prevented per 1,000 women regularly attending screening, and five deaths prevented per 1,000 women invited to screening.

One of the report's authors, Stephen Duffy, professor of cancer screening at Queen Mary University, London, said: "Despite evidence that mammography screening is effective, we still need to carry out further research on alternative screening methods, such as the promising 'digital breast tomosynthesis'; a newly developed form of 3D imaging which could potentially improve the accuracy of mammography in coping with more dense breast tissue."

The experts also looked at the effectiveness of breast cancer screening using physical examination. While they found no evidence of a reduction in breast cancer mortality for women who undertook breast self-examination, they said there is sufficient evidence that breast examination by a health professional can detect smaller and earlier-stage tumours.

Breast cancer is the most frequently diagnosed cancer in women worldwide. It is the second leading cause of cancer death in women in developed countries.

Latest figures from the National Cancer Registry show there are just more than 3,000 new cases of female breast cancer diagnosed annually in the Republic.

Muiris Houston

Dr Muiris Houston

Dr Muiris Houston is medical journalist, health analyst and Irish Times contributor