The Canadian National Breast Screening Study (CNBSS) has reported results of its long term follow-up in the BMJ: no survival benefit of screening mammograms.
To paraphrase Yogi Berra “it’s mammography all over again.”
Is the science settled then?
Before I wade further it’s important to understand what is implied by “settling the science.”
Einstein said “no amount of experimentation can prove me right; a single experiment can prove me wrong.”In physical sciences a theory need only be disproven once for it to be cast aside. Heliocentricity cannot coexist with Ptolemy’s universe. The statement “all swans are white” is disproven by a single black swan.
What do we do with the studies that showed survival benefit of screening mammograms? Why does the CNBSS not close the debate over mammograms, like Galileo did with celestial egocentricity?
The simple and simplistic answer is because there are powerful advocacy groups, special interests; the pink-industrial complex who have a vested interest in undermining the science.
But that lends to conspiratorial thinking. Special interests cannot undermine Maxwell’s equations or Faraday’s laws just because they do not like them.
The testability of Maxwell’s equations is inherently different from verifying that screening mammograms increase life expectancy. We must acknowledge two types of science; the former, physical science, a hard science; the latter, a hybrid of biology and epidemiology, soft science.
Soft science is a misnomer. There is nothing soft about performing a randomized controlled trial (RCT), the methodological gold standard; in ensuring factors that falsely augment or attenuate impact of screening mammograms are evenly distributed, data reliably collected, cause of death accurately recorded and correctly inferred. But the human factor and all its inevitable foibles are unavoidable in soft sciences.