Really? Cancer Screening Doesn’t Save Lives?!
If you’re my age or older, and you’re, like me, something of a rule follower — then you’re getting screened for various cancers.
Colonoscopies, mammograms, cervical cancer screening, chest CTs for people with a significant smoking history. The tests are done and usually, but not always, they are negative. And if positive, usually, but not always, follow-up tests are negative, and if they aren’t and a new cancer is diagnosed you tell yourself — well, at least we caught it early. Isn’t it good that I’m a rule follower. My life was just saved.
But it turns out, proving that cancer screening actually saves lives is actually quite difficult. Is it possible that all this screening is for nothing?
The benefits, risks, or perhaps futility of cancer screening is in the news this week because of this article, appearing in JAMA Internal Medicine.
It’s a meta-analysis of very specific randomized trials of cancer screening modalities, and concludes, with the exception of sigmoidoscopy for colon cancer screening, that none of them meaningfully change life expectancy.
Now — a bit of inside baseball here — I almost never choose to discuss meta-analyses here. It’s hard enough to dig deep into the methodology of a single study, but with a meta-analysis, you’re sort of obligated to review all the included studies, and, what’s worse, the studies that were not included but might bear on the central question.
In this case, though, the topic is important enough to think about a bit more, and the conclusions have large enough implications for public health that we should question them a bit.
First, let’s run down the study as presented.
The authors searched for randomized trials of cancer screening modalities. This is important, and I think appropriate. They wanted studies that took some people and assigned them to screening, and some people to no screening — avoiding the confounding that would come from…