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Mammography Debate Continues

Mammography Debate Continues

The journal Lancet recently published an important
analysis from six physicians at Weill Cornell Medical College (359:404-406,
2002), rebutting an article published in an earlier issue of Lancet
(358:1340-1342, 2001) that cast doubt on the value of mammography in preventing
death from breast cancer. The Weill Cornell authors believe the debate over
breast cancer screening has been misguided and has done a disservice to the
general public, to physicians, and to women specifically. Their hope was that
their latest analysis would reopen and refocus the issue. Indeed, the ensuing
debate has had experts repeatedly change their stand on the value of mammography

Flawed Design

The Weill Cornell team, led by Drs. Claudia Henschke and David Yankelevitz of
the department of radiology and Dr. Olli S. Miettinen of the department of
medicine, pointed out the fundamental flaws in the design of the study that
evaluated the usefulness of mammography screening. One flaw was the mistaken
assumption that screening is supposed to prevent death from cancer almost
immediately after it is performed. In reality, the authors noted, only early
treatment can result in immediate cure, whereas the screening-prevented death
would have occurred several years later.

Another even more fundamental flaw was the failure to include any meaningful
measure of the screening’s usefulness. The purpose of screening for cancer is
to enhance its curability and, thereby, to reduce the risk of death from the
cancer insofar as it develops. This risk is expressed by the cancer’s
case-fatality rate.

Thus, an important measure of any cancer screening’s usefulness is its
resultant proportional reduction in the cancer’s case-fatality rate. The
magnitude of this reduction can be estimated from trials (screening vs no
screening, rather than early vs late treatment) only if they involve
sufficiently long-term screening, and an appreciation of the time lag between
cure and the thereby prevented deaths.

Growing Controversy

Drs. Ole Olsen and Peter C. Gøtzsche were the original authors of the Lancet
meta-analysis that reviewed seven trials of mammographic screening and concluded
that "there is no reliable evidence that screening for breast cancer
reduces mortality." This conclusion was widely noted and publicized. On
December 9, 2001, The New York Times said that "experts and women’s
health advocates . . . do not know what to think about the report." More
recently, another article in the Times reported that, "An independent panel
of experts said today that there was insufficient evidence to show that
mammograms prevented breast cancer deaths."


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