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Archive for November 18th, 2009

The USPSTF recommendations for breast cancer screening: Not the final word

Preface: On issues such as this, I think it’s always good for me to emphasize my disclaimer, in particular:

Dr. Gorski must emphasize that the opinions expressed in his posts on Science-Based Medicine are his and his alone and that all writing for this blog is done on his own time and not in any capacity representing his place of employment. His views do not represent the opinions of his department, university, hospital, or cancer institute and should never be construed as such. Finally, his writings are meant as commentary only and are therefore not meant to be used as specific health care recommendations for individuals. Readers should consult their physicians for advice regarding specific health problems or issues that they might have.

Now, on to the post…

“Early detection saves lives.”

Remember how I started a post a year and a half ago starting out with just this statement? I did it because that is the default assumption and has been so for quite a while. It’s an eminently reasonable-sounding concept that just makes sense. As I pointed out a year and a half ago, though, the question of the benefits of the early detection of cancer is more complicated than you think. Indeed, I’ve written several posts since then on the topic of mammography and breast cancer, the most recent of which I posted a mere two weeks ago. As studies have been released and my thinking on screening for breast cancer has evolved, regular readers have had a front row seat. Through it all, I hope I’ve managed to convey some of the issues involved in screening for cancer and just how difficult they are. How to screen for breast cancer, at what age to begin screening, and how to balance the benefits, risks, and costs are controversial issues, and that controversy has bubbled up to the surface into the mainstream media and public consciousness over the last year or so.

This week, all I can say is, “Here we go again”; that is, between downing slugs of ibuprofen for the headaches some controversial new guidelines for breast cancer screening are causing many of us in the cancer field.
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Posted in: Cancer, Diagnostic tests & procedures, Politics and Regulation, Public Health

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Evidence in Medicine: Correlation and Causation

There are two general approaches to subverting science-based medicine (SBM): anti-science and pseudoscience. Anti-scientific approaches are any that seek to undermine science as the determinant of the standard of care, often overtly advocating for spiritual or subjectively-based standards. Some attack the validity of science itself, usually with post-modernist philosophy.

Pseudoscientific proponents, on the other hand, praise science, they just do it wrong. In reality there is a continuum along a spectrum from complete pseudoscience to pristine science, and no clear demarcation in the middle. Individual studies vary along this spectrum as well – there are different kinds of evidence, each with its own strengths and weaknesses, and there are no perfect studies. Further, when evaluating any question in medicine, the literature (the totality of all those individual studies) rarely points uniformly to a single answer.

These multiple overlapping continua of scientific quality create the potential to make just about any claim seem scientific simply by how the evidence is interpreted. Also, even a modest bias can lead to emphasizing certain pieces of evidence over others, leading to conclusions which seem scientific but are unreliable. Also, proponents can easily begin with a desired conclusion, and then back fill the evidence to suit their needs (rather than allowing the evidence to lead them to a conclusion).

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Posted in: Science and Medicine

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