Better Health: Smart Health Commentary Better Health (TM): smart health commentary

Article Comments

Have Mammograms Delivered Their Promised Effect?

A well-done analysis in the BMJ this week calls into question previous research that has been used to tout mammography as an effective tool for lowering breast cancer mortality in Denmark.  That previous study compared breast cancer death rates in Copenhagen, where women were offered screening mammography in 1991, to areas in Denmark where mammograms were not offered until 17 years later, and concluded that the introduction of mammogram screening resulted in a 25 % reduction in breast cancer mortality in screened areas.

The new study adds an additional county where screening was offered (with a little implication that perhaps the previous researchers should have included this other area, but I’ll stay out of the academic finger pointing) and then reanalyzes the data. 

The researchers found that breast cancer deaths declined nationwide during the time period studied, in all areas, regardless if that area was one offering the screening program. Much of this decline occurred in women ages 40-49, who were too young to have been offered screening. This suggests that it is breast cancer treatment rather than screening that should take the credit for most of the mortality declines in Denmark over the time period studied.

The researchers then go on to make this statement:

We believe it is time to question whether screening has delivered the promised effect on breast cancer mortality.

This practically guaranteed that I’d have to read their paper and comment on it. So I am.

My take

I’m not convinced that this paper makes the point that mammograms are ineffective. The authors themselves argue that the effect size of mammography, estimated at about 15-16% in randomized trials, is too small to be measured in epidimiologic studies. I  agree. It is just impossible to control all the confounding factors inherent in an entire population of individuals to tease out the effect of a single intervention over time, particularly when breast cancer treatment was evolving so rapidly over the time period being studied.

I have to admit that I have a hard time believing that, for 17 years, women living outside of Copenhagen never entered that fair city to have a mammogram on their own dollar once they found out that their city-dwelling friends were being offered the test and they weren’t. (The paper used to support the claim doesn’t make the case in my opinion.) I know that Europeans have not bought the whole mammogram thing hook, line and sinker the way we here in the States have, but I don’t think it is as black and white as the Danes would like us to believe. (If you are a Danish woman reading this, feel free to enlighten us…) But that’s just an aside.

Bottom Line

This is an important paper in that it effectively refutes previous conclusions about the Danish mammogram screening program. Unfortunately, I don’t think this study stands on any stronger ground in arguing that mammograms are ineffective. Nothing in this paper rescinds the results of the randomized trials, which the authors themselves state find a mortality reduction of about 15-16% for mammography. In my opinion, their results primarily show us that population based data is nearly impossible to use to make any valid conclusions about mammogram screening — either for or against it.
_________________________________________________

Hat tip to Gary Schwitzer for pointing me to this study

*This blog post was originally published at The Blog that Ate Manhattan*


You may also like these posts

Read comments »


Comments are closed.

Return to article »

Latest Interviews

IDEA Labs: Medical Students Take The Lead In Healthcare Innovation

It’s no secret that doctors are disappointed with the way that the U.S. healthcare system is evolving. Most feel helpless about improving their work conditions or solving technical problems in patient care. Fortunately one young medical student was undeterred by the mountain of disappointment carried by his senior clinician mentors…

Read more »

How To Be A Successful Patient: Young Doctors Offer Some Advice

I am proud to be a part of the American Resident Project an initiative that promotes the writing of medical students residents and new physicians as they explore ideas for transforming American health care delivery. I recently had the opportunity to interview three of the writing fellows about how to…

Read more »

See all interviews »

Latest Cartoon

See all cartoons »

Latest Book Reviews

Book Review: Is Empathy Learned By Faking It Till It’s Real?

I m often asked to do book reviews on my blog and I rarely agree to them. This is because it takes me a long time to read a book and then if I don t enjoy it I figure the author would rather me remain silent than publish my…

Read more »

The Spirit Of The Place: Samuel Shem’s New Book May Depress You

When I was in medical school I read Samuel Shem s House Of God as a right of passage. At the time I found it to be a cynical yet eerily accurate portrayal of the underbelly of academic medicine. I gained comfort from its gallows humor and it made me…

Read more »

Eat To Save Your Life: Another Half-True Diet Book

I am hesitant to review diet books because they are so often a tangled mess of fact and fiction. Teasing out their truth from falsehood is about as exhausting as delousing a long-haired elementary school student. However after being approached by the authors’ PR agency with the promise of a…

Read more »

See all book reviews »