For decades, improvement in diagnostic tools for cancer have led to a movement of early screening from mammograms to colonoscopies. Today, Dr. Otis Brawley, a Johns Hopkins Bloomberg Distinguished Professor, tells Stephanie Desmon that many people think screening is better than it actually is. While early screening can save lives, they discuss the how to be sure you're getting high-quality screening when you need it, and about some of the harm of over-screening in certain cases.