A Bit More on False Positives, Dec 2009, Part 1
The question of false positives in breast cancer screening – why and how these happen, how often these occur, and how much these cost, in physical, psychological and financial terms – remains a puzzle.
A few weeks ago the New York Times Magazine featured a piece on “Mammogram Math” under the heading “The Way We Live Now.” The author, a mathematics professor, argues that the risks and costs of mammography, though incalculable, outweigh the benefits. The paper printed the article along with a subtitle, “Why evidence-based medicine is actually right and scary” and later published three letters including one truncated response by me.
After a hiatus, I’ve rescanned the literature – just to be sure the question hasn’t been resolved in the past few weeks by a much-needed interdisciplinary team of health care policy experts, economists, statisticians, surgeons, radiologists, oncologists, nurses and for good measure, perhaps a few breast cancer patients and survivors.
There’s little published progress to report, aside from more hype and theoretical numbers such as I offered in a November essay. So I’ve decided to take the analysis a step further by outlining a tentative framework for thinking about false positives in breast cancer screening.
In a separate post, I will outline a proposed outline for categorizing false positives as they relate to mammography. Why bother, you might ask – wouldn’t it be easier to drop the subject?
“Make it go away,” sang Sheryl Crow on her radiation sessions.
Instead, I’ll answer as might a physician and board-certified oncologist who happens to be a BC survivor in her 40s:
To determine the damage done to women by screening mammography (as some claim and refer as evidence) we need establish how often false positives lead, in current practice, to additional procedures such as sonograms (fairly often, but the costs are relatively small), MRIs (less standard and more expensive), breast biopsies (scarier, slightly risky and more valued – how else can a pathologist determine if a woman with a breast lesion has cancer and, in the future, what type of therapy is best) or frankly inappropriate treatments such as chemotherapy for a non-cancerous condition (very damaging and the most costly of all putative false positive outcomes).
These numbers matter. They’re essential to the claim that the risks of breast cancer screening outweigh the benefits.
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