Political interpretation of scientific evidence--case study of breast cancer screening policies around the world.

Early detection of breast cancer has been studied for effectiveness in reducing mortality for more than four decades. During this period numerous studies took place, with more than half a million participating women. In spite of large amounts of nonconflicting data, different countries took varying lengths of time to establish a policy, and came up with a variety of policies, quite different from one another. Inherent differences between the countries in structure of the health system, in the commitment to public health activities, and in opinions and health habits of the relevant populations may explain these different outcomes.