from a recent NY Times Article:
Researchers took advantage of a natural experiment in three pairs of countries. Some had instituted regular mammography screening significantly earlier than the others, but their health care systems and socioeconomic levels were nearly identical. The countries matched for comparison were Northern Ireland and the Republic of Ireland; the Netherlands and Belgium; and Sweden and Norway.
The study, published online July 28 in the British medical journal BMJ, found that in all three cases, earlier implementation of screening had no effect on mortality. For example, in Northern Ireland, screening was introduced in the early 1990s, and by 1995, 75 percent of the women were getting mammograms. In the Republic of Ireland, screening was not introduced until 2000, and it was not until 2008 that 76 percent of the population was screened. Yet from 1989 to 2006, breast cancer mortality decreased by 29.6 percent in Northern Ireland and by 26.7 percent in Ireland.
“We were surprised and quite sad to find that breast cancer screening doesn’t work,” said Dr. Philippe Autier, the lead author. “We were expecting to find the reverse.”