Patients and their doctors count on cancer screening tests to save lives, and yet a number of large, controlled studies are showing disappointing results for mammography and other mass screening tests.

This month, the New England Journal of Medicine published a controversial study that cast doubt on the widely accepted benefits of colonoscopy.

The take-home lesson from these disappointing trials isn’t that we should abandon early screening. It’s still the best hope we have of reducing the high toll of death and suffering caused by cancer — which claims about a half a million lives a year in the U.S. alone.