Breast screening by mammography has been introduced into many countries over recent years. Breast screening is a big investment and so we need evidence that it provides real value for healthcare money – in terms of reduced mortality from breast cancer. You might expect that catching cancers early through breast screening is sure to reduce mortality, because women can be treated for their disease much earlier. For mammography picks up tiny tumors long before a woman could detect a problem herself.

However a new study, from Denmark, now casts doubt on the value of breast screening programs. In 2005, a study suggested that breast screening had reduced breast cancer deaths in Copenhagen by as much as 25%. But the study was thought to have some problems and the conclusions were in doubt. Therefore, scientists at the Nordic Cochrane Center and elsewhere decided to take another look and carried out a more comprehensive analysis of breast screening data.

They looked at annual changes in breast cancer deaths in two regions of Denmark that have breast screening and compared these with deaths in regions that don’t offer breast screening. They split data for the area into three age bands: 55-74 (women who stood to benefit from breast screening, 35-54 (not affected by breast screening because too young) and 75-84 (too old to benefit from breast screening). They looked at the 10 years after which breast screening could have had an impact on breast cancer mortality. And, for comparison, they also looked at the 10 year period before breast screening was introduced.

In the 55-74 age group, breast cancer mortality went down 1% in screened areas but by 2% in non-screened areas. In women too young to benefit from breast screening, mortality went down 5% in screened areas and 6% in non-screened areas. For the older ages, there was no real difference in breast cancer mortality between screened and non-screened areas. The researchers believe that declines in breast cancer mortality are due to changes in risk factors and earlier and/or more effective treatment. Since breast screening seems to have no impact, it may be time to rethink whether these programs really have any value on women’s long term health.

Source:

Jørgensen K et al BMJ Online First 24^th March 2010 BMJ 2010:340;c1241