Monday, May 27, 2013


Several studies have disputed the efficacy of mammograms. I, being a man, of course ignored these when they hit the news last year. Some friends were discussing it, which got me thinking, "How could getting mammograms not help?"

Here are two articles which discuss the changing science on mamography:

  • (link
  • (link)
The first indicates that screening does not correlate with reductions in breast cancer mortality rates. Also, screening tends to find cancers that "would not have harmed them". The second reinforces that "that screening mammography doesn’t save lives" and "the number of cancers diagnosed at the advanced stage was essentially unchanged".

I thought about this for a while. How could screening mammograms, which find early stage cancer, not reduce advanced stage cancers or cancer deaths? I came up with five reasons:
  1. The early cancers detected would not have become malignant, so finding and treating them doesn't affect mortality rates.
  2. The early cancers that may have become malignant would have been caught at a later time. Treatments are now so advanced that the delay doesn't appreciably affect the mortality rate.
  3. Other screening methods are finding cancers so mammogram screening is less effective at finding cancer. Maybe women who do self exams find more cancers compared to women who wait for their yearly mammograms. This would strangely lead to a correlation between mammograms and increased mortality rates.
  4. The treatments may negatively affect mortality. Getting surgery or radiation or chemotherapy on early cancers or benign cancers may damage health enough to outweigh any benefits. I couldn't find a clear answer whether the mortality rates were just due to cancer, or due to anything (I'm guessing the latter).
  5. The advanced cancers appear very quickly and are very deadly. This makes some sense because cancer is uncontrolled growth of previously normal cells. Fast growing cancers would seem to be the most deadly. In this case, the mammography screening rate might have to be monthly to have a hope of finding these advanced cancers in time to make a large difference in mortality.
        I decided to actually read the original New England Journal of Medicine article, so see if I could understand what was going on.
        It enlightened the situation, and also showed the difference between scientists and science journalists. Here are some quotes for the NEJM study Discussion section:
        • "Over the same period, the rate of death from breast cancer decreased considerably. Among women 40 years of age or older, deaths from breast cancer decreased from 71 to 51 deaths per 100,000 women — a 28% decrease. This reduction in mortality is probably due to some combination of the effects of screening mammography and better treatment. Seven separate modeling exercises by the Cancer Intervention and Surveillance Modeling Network investigators provided a wide range of estimates for the relative contribution of each effect: screening mammography might be responsible for as little as 28% or as much as 65% of the observed reduction in mortality (the remainder being the effect of better treatment). Our data show that the true contribution of mammography to decreasing mortality must be at the low end of this range."
        • "As treatment of clinically detected disease (detected by means other than screening) improves, the benefit of screening diminishes"
        • "Women now widely recognize the significance of a new breast lump and the need for diagnostic mammography. Ironically, increased awareness confers less opportunity for screening mammography to reduce the incidence of advanced cancer. ... We agree that women should understand that screening raises their risk of becoming a patient with breast cancer and that there is uncertainty about the benefit of screening. The assessment of how to cope with that uncertainty, however, remains a value judgment that we believe should be left to women and their doctors." - Authors response in Letters section
        It should also be noted that the study did not follow women to see what they were doing, but looked at general statistics. It did not look at a woman's family risk of breast cancer, or whether they did self exams. Also, some fairly large adjustments had to be made to account for hormone-replacement therapy's effect on cancer rates.

        What I take away from this is screening, in all forms, is useful, but results should be reflected on before health-affecting treatments are begun to make sure they are necessary. But this is a complicated subject, and my heart goes out to anyone who has to deal this these issues.

        1 comment:

        AT said...

        Hey, thanks for posting this. And good on you for going to the source -- I had wrongly assumed the study would be behind a paywall or university-wall so I didn't explore any further.

        I couldn't find a clear answer whether the mortality rates were just due to cancer, or due to anything (I'm guessing the latter).

        This is what I gather too. The criticism I've been following (and these are not the only two articles on the subject I've ever read, they were just the ones that a quick Google search turned up in the context of our discussion) has been drawing a distinction between people who die WITH a disease and people who die OF it. If I were diagnosed with a disease that, left to its own devices, would kill me in 80 years, then I sure as shit wouldn't go in for invasive treatments for it. Or if I were 80 years old and diagnosed with a disease that would kill me in 10 years, I would very strongly consider letting that disease run its course, since 10 (or 9, or 8) years out of a hospital sounds better to me than 15 (or 17, or 20) years in it.

        Now obviously things are more complicated than that, as you well know -- the "quality of life" calculus is pretty complex when you have a disease that affects your life in a thousand small ways. And of course different people have different definitions of "invasive"; people are going to draw the line in different places between the extremes of "taking a pill once in a while" to "months of chemo."

        The problem, as I see it, is that overdiagnosis takes a lot of that power out of the hands of the person with the illness: the sad truth is that as soon as a problem (any problem) is discovered, the default reaction is to treat it as aggressively as possible. Overdiagnosis/overtreatment is a huge issue, especially in the U.S., not just for breast cancer but for just about anything. Overtreatment causes stress, a whole host of secondary risks (which may cause some of those earlier deaths), and massive expense for both the individual and the public purse, and I'm not always convinced of its usefulness in improving health. As you say, if these cancers would have caused fewer problems than radiation treatment does, then it's time to pump the brakes.

        So if I'm touchy about mammograms it's part of a larger concern with a cure that in many cases is demonstrably worse than the disease itself, and a cure that women are often not permitted to turn down once the results are in.

        results should be reflected on before health-affecting treatments are begun to make sure they are necessary.

        On this we are 100% in agreement. I don't think we're there yet, culturally, though there are some heartening signs that patients are (slowly, slowly) getting more information about their conditions and more say in how they are treated. This is gendered, too: women are only JUST starting to get out of an era of extremely patronizing and humiliating treatment in doctors' offices, and the public dialogue about breast cancer continues to be disgustingly infantilizing and sexualizing (remember Komen?). I'm very lucky to have had GP's my whole life who made me feel like a valuable contributor to my own diagnosis and treatment, but even I have stories that'll chill your blood. So if I have some suspicions about what will happen to my mammogram results, I think they're earned. :(

        Thanks again for writing this post.