In some cases, the only thing that detection of non-symptomatic cancer does is turn someone into a cancer patient who's tumor would otherwise never threaten their health or effect mortality. The more cancer you look for the more cancer you find.
>What’s clear is that cancers fall into a few general behavior patterns, which Welch and others have compared to animals that must be kept in the barnyard to prevent a deadly rampage. Papillary tumors are like turtles — they move very slowly and never pose an escape risk. They don’t need screening, because they will never cause trouble. Then there are rabbits, which are eager to hop away to other parts of the body, but can be confined if they’re found and fenced. These are the cancers that can be helped by early detection and treatment. Birds, on the other hand, are so flighty and quick that they can’t be confined. Screening makes no difference for bird cancers, because they’re so aggressive that they can’t be detected before they’ve begun their deadly course.
>No cancer screening has ever eliminated the majority of cancer deaths. Instead, the best screening can do is reign in the rabbits. Birds remain unstoppable, and they’re the ones responsible for most cancer deaths. This is why, Welch says, three decades of mammography have failed to put a dent in the rate of women presenting with metastatic breast cancer upon their initial diagnosis. Women with breast cancers that behave like birds will almost never be helped by a mammogram, nor will men with the most aggressive prostate cancers be saved by PSA tests.
