For the Fall 2016 issue of Cancer Today, I spoke with epidemiologist Pam Marcus on why cancer screening can have risks.

As my article notes, the premise of cancer screening seems straightforward: Save lives by finding cancers before they start causing symptoms, when they are smaller and often easier to treat.

But as scientists have learned more about how tumors grow and spread, the road from cancer screening to saving lives has taken unexpected twists and turns. Some cancers spread to other parts of the body while still small. Others are so aggressive that finding them early doesn’t change the outcome. And still others might never need to be found, or treated, at all.

This doesn’t mean cancer screening has no value. But it does mean that potential benefits must be weighed against risks. Read the full Q&A.