The latest study to show that screening mammography has very little or no benefit for average risk women, and that it causes a great deal of cost due to unnecessary tests and treatment, came as a shock to everyone who was unaware of the fact that the evidence already suggested that. The mortality benefits might be a little bit on the positive side, but not enough to justify the enormous costs, which includes causing some excess mortality. (Note: “average risk” means “on average, when employed by the entire population”, which leaves open the possibility that identifiable high-risk groups might still benefit.)
The illusion that screening is beneficial comes largely from the fact that it detects a lot of biological cancers that never would have caused disease if left undetected, and thus — viola! — it creates a lot of people who had their cancer detected and survived. More subtly, screening detects those cancers that are destined to cause disease earlier, and thus “survival time” (measured in terms of time since detection, rather than when the bad outcome actually occurred in someone’s life, which is obvious what matters) is longer even when there is no benefit from detection.
But what is really annoying me is all the lamenting that this is bad news (example). It is not. It is good news.
Breast cancer mortality rates are what they are. If it turns out that they would be exactly the same without spending billions of dollars on screening — to say nothing of the pain and suffering, and the cancers that are actually caused by the radiation — then mortality risks can stay the same and we can save billions of dollars by ending the worthless effort.
Finding out that you have been doing something that was costly and harmful is annoying and perhaps embarrassing. But it should not be hard to understand that it is good to discover it, not bad, and that correcting the error is a benefit, not a cost. (Except, of course, to the industry that has been getting rich off it.)
Enough said, I hope.
EP-ology 