Odgovor To jan 23, 2018 08:01

Why cancer screening has never been shown to “save lives”

Why cancer screening has never been shown to “save lives”—and what we can do about it

The claim that cancer screening saves lives is based on fewer deaths due to the target cancer. Vinay Prasad and colleagues argue that reductions in overall mortality should be the benchmark and call for higher standards of evidence for cancer screening

Despite growing appreciation of the harms of cancer screening,1 2 3 advocates still claim that it “saves lives.”4 This assertion rests, however, on reductions in disease specific mortality rather than overall mortality.

Using disease specific mortality as a proxy for overall mortality deprives people of information about their chief concern: reducing their risk of dying.5 6 Although some people may have personal reasons for wanting to avoid a specific diagnosis, the burden falls on providers to provide clear information about both disease specific and overall mortality and to ensure that the overall goal of healthcare—to improve quantity and quality of life—is not undermined.7

In this article we argue that overall mortality should be the benchmark against which screening is judged and discuss how to improve the evidence upon which screening rests.
Why cancer screening might not reduce overall mortality

Discrepancies between disease specific and overall mortality were found in direction or magnitude in seven of 12 randomised trials of cancer screening.8 Despite reductions in disease specific mortality in the majority of studies, overall mortality was unchanged or increased. In cases where both mortality rates were reduced the improvement was larger in overall mortality than in disease specific mortality. This suggests an imbalance in non-disease specific deaths, which warrants examination and explanation. A systematic review of meta-analyses of cancer screening trials found that three of 10 (33%) showed reductions in disease specific mortality and that none showed reductions in overall mortality.9

There are two chief reasons why cancer screening might reduce disease specific mortality without significantly reducing overall mortality. Firstly, studies may …

http://www.bmj.com/content/352/bmj.h6080
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