Mammography screening can cut breast cancer deaths by about 28%, according to a new study.
The latest findings, from Norway, follow repeated controversy about the benefits of screening.
"Methods used by some of the original trials have been criticised, and a report from the Cochrane Collaboration considered the estimates of mortality benefit from many of those trials to be invalid," write Dr Harald Weedon-Fekjaer of the Norwegian University of Science and Technology, and colleagues in the British Medical Journal.
They looked at the effectiveness of mammography screening using nationwide figures on Norwegian women from 1986 to 2009. A national mammography screening programme was gradually brought in from 1995 to 2005 for women aged 50 to 69 years.
During the full period from 1986 to 2009 there were 1,175 breast cancer deaths among women diagnosed after being invited to screening, and 8,996 among women diagnosed before being invited to screening.
Being invited to mammography screening was linked with a 28% drop in risk of death from breast cancer, once many factors such as age were taken into account. The researchers calculate that, to prevent one death from breast cancer, 368 women would need to be invited to screening.
Commenting on the study in an editorial, Dr Joann Elmore of the University of Washington, USA, says that the findings should "make us reflect on how to monitor the changing benefits and harms of breast cancer screening."
She adds that: "Careful assessment of ongoing screening programmes is required. In the meantime, make yourself comfortable – this may take a while."
Weedon-Fekjaer, H. et al. Modern mammography screening and breast cancer mortality: population study. BMJ 18 June 2014; doi: 10.1136/bmj.g3701 [abstract]
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