Breast Cancer Trends: A Marriage Between Clinical Trial Evidence and Epidemiology.

The article comments on a paper which reports the changes in screening mammography, menopausal hormone therapy, and breast cancer incidence in the Kaiser Permanente Northwest health plan. The authors stress that the researchers have failed to consider on what causes the decline in incidence between 2000 and 2004. A randomized trial is considered not helpful in population studies. The authors also emphasize that the paper is not done at the level of individual patient data.