A recently-released case control study failed to find a mortality benefit for mammograms:

A real-world look at the benefits of breast cancer screenings has turned up some dismaying news: Screening rates for women who died from the disease were no different from the screening rates of those who were cancer-free.

The U.S. researchers who conducted the study, however, hastened to add that women should not stop getting routine mammograms and clinical breast exams based on these findings.

Contrary to popular belief, one cannot assume that all screening tests lead to a decrease in mortality. I like how the researchers try to explain their findings:

This new data comes from real-world situations, and Elmore believes one reason the results fall short of ideal is that the quality of community screenings is lower than those typically used in clinical trials.

Uh, not everyone has access to the resources in clinical trials. If anything, results based on community studies should be weighted more heavily, since they represent the tests the majority receive. (Doheny, "Study: Mammos May Not Halt Breast Cancer Deaths", Forbes, Jul.19)