In mammography discussion, the plural of anecdote is not data

I can’t tell you how many times I’ve used that line in interviews recently.

So it was refreshing to see someone else – Steven Pearlstein – use it today in the Washington Post. (* Actually, either he or the copy desk butchered the quote, leaving out the “not.” Surely they meant well, but the quote and the point makes no sense without it, and indeed, is NOT what the standard line is. I’ve added it in the following excerpt with a * and hope the Post corrects this soon.)

“I should acknowledge that I have no idea who should and should not get routine mammograms. But I know enough about statistics to say that the issue is not settled just because you know of someone in her 40s whose breast cancer was detected by a mammogram and cured. As economists and medical researchers are fond of saying, the plural of anecdote is *(not) data. …

As is often the case in such matters, those raising the most fuss were those with greatest financial interest in mammography (the radiologists and the makers of mammography machines) and the disease groups (in this case, the American Cancer Society), which tend to resist recognizing limits on how much time, money and attention is devoted to their cause.

“How many mothers, sisters, aunts, grandmothers, daughters and friends are we willing to lose to breast cancer while the debate goes on about the limitations of mammography?” Otis Brawley, chief medical officer of the American Cancer Society, asked in an op-ed article in Thursday’s Washington Post. Dr. Brawley cleverly didn’t answer his own question, but the clear implication of his question was that the only acceptable number should be zero. And it is that very attitude, applied across the board to every patient and every disease, which goes a long way in explaining why ours is the most expensive, and one of the least effective, health-care systems in the industrialized world.”

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Dr. Kathleen T. Ruddy, Founder and President, Breast Health & Healing Foundation

November 21, 2009 at 7:58 am

Anecdotes DO make data, you just don’t find them in the middle of the preponderance of the data, you find them as outliers … or, as Nassim Taleb so aptly describes them, as Black Swans. In fact, you learn more from Black Swans than you do from the data that is amassed squarely under the Bell Curve, but this is not the fast-track to understanding of why outliers occur, it is a slow slog through mystery and confusion. Nevertheless, as Neils Bohr would say, (paraphrasing): it is in the conflict that the truth will be found.
Mammograms do save lives, at every age. Furthermore, at the present time, mammograms are the only effective screening tool we have that prevent deaths from breast cancer. The problem is that they fall very short of the mark as regards cost-effectiveness, sensitivity, positive predictive value, specificity etc. And they tend to lead to a whole cascade of (retrospectively) unnecessary tests — not what you want in a good screening test.
We need a better screening test for breast cancer. Fortunately, many are working hard to find one. In the meantime, I don’t think it makes sense to abandon or reduce the application of the ONLY screening test we have for the early detection of breast cancer – a test that everyone agrees does (in fact) save lives – UNTIL we can offer a substitute.
There is too much breast cancer, there are too many lives that are lost to breast cancer, to pull back to zero screening for women in their 40’s and biannual screening for women over 50 just because mammographic screening leaves much to be desired. There is not a woman alive, who has had a mammogram, who is not well aware of this fact.
Stick with annual mammographic screening, beginning at age of 40, and work overtime to find a better screen, as soon as possible.

Gary Schwitzer

November 21, 2009 at 8:16 am

Dr. Ruddy,
I posted your comment, but must challenge even the hint of an assertion that this week’s USPSTF recommendations call for “abandoning” mammography. That’s what you suggested in your comment and that is inaccurate and unfounded.