Depends on the risk of the person - some need it every 5 (or more), and some much earlier than 40. But generally speaking, it takes ~10 years (average) for an i

Depends on the risk of the person - some need it every 5 (or more), and some much earlier than 40. But generally speaking, it takes ~10 years (average) for an initial growth to become "fully" cancerous. Hence the 10 year rec. Still - point is this is one of the few forms of cancer that can be treated extremely (simple exicision) easily with early detection. Its common and (once advanced) deadly.