Mammography screening has cut the number of deaths from breast cancer by almost half, according to studies of screening programmes in two European countries.

The first study compared deaths from breast cancer diagnosed in two Swedish counties in the 20 years before screening was introduced, 1958 to 1977, with the 20 years after, 1978 to 1997 (Lancet 2003;361:1405-10). The study, which included 210000 women, showed that the unadjusted risk of death from breast cancer dropped after the introduction of screening by 23% in women aged 40–69 years (relative risk 0.77 (95% confidence interval 0.70 to 0.85; P<0.0001)).

The reduction in this age group was …