Horribly depressing news about mammograms – ctd.

I’m getting a lot of emails claiming that the mammogram study was flawed. I’m totally swamped today, but I feel compelled to try and respond quickly to some of the complaints. They come in a few flavors:

1) The mammogram technology used in this study was flawed, sucked, and is worse than that of today. Ok, this will always be a complaint against any study, but let’s play this out. One of the things that makes this study better is that it’s one of the few that exists in the more modern era of treatment, when therapy is better. Most of the studies that show a benefit to mammography are older. In other words, the technology used in those studies was even worse. So people are basically saying that they trust the results from studies of mammography with ever crappier technology than this one. That’s odd.

Moreover, one of the major problems was overdiagnosis. I don’t think that being able to see more tumors was the biggest problem with the technology. This was the 1990’s, not the 1800’s.

2) The randomization process was biased and violated some tenets of randomized controlled trials. This one is bizarre to me. It almost feels like they’re accusing the researchers of lying. Let me quote directly from the manuscript:

Participants then had a physical (clinical) breast examination and were taught breast self examination by trained nurses, or in the province of Quebec, by doctors. The examiners had no role in the randomisation that followed; this was performed by the study coordinators in each centre. Randomisation was individual and stratified by centre and five year age group. Irrespective of the findings on physical examination, women aged 40-49 were independently and blindly assigned randomly to receive mammography or no mammography.

Short of actual evidence of fraud or of breaking the protocol, these accusations of sending women with concerns to the mammogram group seem unfounded.

3) Women in the control group were taught self-exam and were therefore better cared for than actual “no care”. In other words, people are claiming that the women in the no mammogram group don’t represent the real world. They’re arguing that we need to use mammograms because in the real world, women don’t get the care and exams that they got in this study.

First of all, I don’t know if this is true. But it’s an argument for us to do a better job teaching women to do self-exams and go to checkups. Since that performs as well as mammograms, is cheaper, and involves no radiation, why would that not be a better choice? Seems awfully odd to just throw up our hands and just go with a more expensive and more harmful alternative that isn’t superior.

Bottom line: no study is perfect, and we should consider the limitations of all studies when interpreting their results. But if you do 25-year follow up, the technology at the start of the trial will always be older. People in studies never perfectly match what’s happening in the real world. And there’s always a measure of trust in science. You should consider the biases and conflicts of all involved, including the people attacking the study.

I leave you with one final thought. If you’re not going to be swayed at all by a randomized controlled trial of 90,000 women with 25 year follow up, excellent compliance, and damn good methods, it might be time to consider that there’s really no study at all that will make you change your mind.


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