Map of life expectancy at birth from Global Education Project.

Tuesday, August 02, 2011

You're probably sick of this topic by now . . .

Screening mammography, that is. (Yep, let's get back on topic here.) It's a tough subject because a lot of women are convinced that screening saved their lives. They got screened, it found a lesion diagnosed as cancer, they had surgery and possibly chemotherapy and radiation, and now they're alive and they don't have cancer. QED.

But, as I have explained here many times, it ain't necessarily so. Most of the lesions found by screening are small and non-invasive and nobody knows which of them might go on to cause a problem in the future. Many of them, we now understand, simply disappear on their own. In addition to overtreatment of what would have been harmless lesions (not necessarily correctly called cancer in all or even most cases, although that term is normally used), screening results in false positives resulting in further investigation, expense, and anxiety, and just costs time and money to begin with.

The conventional wisdom in the U.S. is that, on balance, it's worth it and does save lives. But how much worth it, and for whom, and how often, has been controversial -- a controversy that has gotten inappropriately nasty. Let me point out that the American Cancer Society and the various physician and surgeon groups that weigh in on this all have a vested interest in finding and treating more tumors. (The ACS gets big-time funding from drug companies.)

So, for what it's worth, the differential timing of wide-scale implementation of mammographic screening in various European countries created a natural experiment, which these investigators have now analyzed. It turns out that there is no apparent relationship whatsoever, at the population level, between general screening mammography and the death rate from breast cancer.

I mean none. Zip, zilch, nada. Death rates from breast cancer have steadily declined in Europe and the U.S. for some 40 years, but the introduction of screening mammography had no evident effect in the countries in this study. By the way, similar comparisons have shown cervical cancer screening to be highly beneficial, so this kind of study can indeed have a different outcome. But, in the case of mammography, it is what it is.

As always, I'm not a real doctor, and I'm certainly not your doctor, and you should do what you think is best. But the evidence for recommending mass screening of women by mammography continues to be highly conflicting at best and there is certainly, in my view, no compelling case for it. More selective use of mammograms, among women at elevated risk, would seem to be the policy with better support, although these studies appear to call even that strategy into question. Hmm. (Note how little attention this study received in the U.S. Whatever the truth may be about this matter, we don't want to be confused with the facts.)


C. Corax said...

Darn, I missed this post. With great ill-will, I dragged myself to my annual mammogram on the 3rd. Why every year? Why not every other year? I did like the tech, though. We had a good chat.

Cervantes said...

Well, I don't know your age or risk factors. Talk to your doctor.