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Wednesday, November 18, 2009

Evidenced based medicine vs. Politically based medicine

The latest blow up regarding the Preventative Services Task force recommendations on mammography should dispel any doubts about our ability to create a firewall around "evidenced based medicine" to prevent decisions from being politicized. Politics always trumps reason. However, many of the assumptions underlying health care reform are undermined by this observation.

It is commonly accepted that health care is a basic human entitlement which should be guaranteed by legal protection. In order for this right to attain such a status, we need to be in the position to define what the scope of the right should be. Presumably, this definition should be based upon what is rational and beneficial to patients. How hard can that be?

The mammography screening controversy underscores how difficult this process is. Few areas have been as well studied for as long as the effectiveness of mammography for preventing breast cancer death. Much of the criticism of the Task Force's recommendations have focused on the perception that their recommendations were solely based upon financial considerations, implying that the only reason not to screen are because it is just too expensive to screen in the younger age groups. This is not an accurate assessment of their work. The full report can be found at http://www.ahrq.gov/clinic/3rduspstf/Breastcancer/bcscrnsum1.htm.

There is much more to the story than money. First, the underlying data does not inspire great confidence in the utility of mammography to save lives. The number of subjects to screen over 10 years to save one life in the 50-60 age group is estimated to be around 1300 with the confidence intervals ranging from about 300 to over 7000! The number to screen in the 40-50 age group was ~1900 with an only slightly smaller confidence interval (900 to 6000). I have to wonder if this data is EVER presented to patients when screening is placed in front of them as an option. What this essentially means is that for any given primary care physician over their entire practice lifetime they could order literally thousands of screening mammograms and they may be saving no lives whatsoever.


When you start to compare numbers from various studies, they just do not add up. For example, in a study by Rowan T. Chlebowski, M.D., Ph.D., Harbor–UCLA WHI Clinical Center, published in 2008 findings from the WHI Estrogen plus Progestin (E+P) Hormone Trial. Of the 16,608 women enrolled in the E+P Trial, 8,506 were randomly assigned to take active study pills with combined estrogen plus progestin, while 8,102 took inactive placebo pills. Each woman had a mammogram and breast examination yearly. Biopsies were performed based on their physicians’ clinical judgment.

During the 5.6 years of the trial, 199 women in the active hormone group and 150 women in the placebo group developed breast cancer. Assuming the rate of cancer formation is relatively constant, one can extrapolate that about 300-400 women will develop cancer over the 10 year window. Given the meta-analysis of the Preventative task force where you need to screen about 1500 women on average for 10+ years to save one life, this would suggest that screening would have saved around 4-6 women in each of these roughly 8000 women cohort. What about the other 150-200 women? Does that mean that all the remaining women's lives, who were diagnosed and treated for breast cancer, were not saved?

At least part of the explanation may be the explosion in the diagnosis of ductal carcinoma in situ (DCIS), which is clearly a consequence of increased screening intensity. As noted in the PSTF report;

"some view diagnosis and treatment of ductal carcinoma in situ (DCIS) as potential adverse consequences of mammography. There is incomplete evidence regarding the natural history of DCIS, the need for treatment, and treatment efficacy, and some women may receive treatment of DCIS that poses little threat to their health. In a 1992 study, 44 percent of women with DCIS were treated with mastectomy and 23 percent to 30 percent were treated with lumpectomy or radiation. In one survey, only 6 percent of women were aware that mammography might detect nonprogressive breast cancer."


Using common funds to pay for screening activities hides the fact that each of us is assuming part of the cost for this. It is a common foil to say that you cannot put a cost on a life saved. There are at least two flaws with this reasoning. First, the evidence of lives saved is marginal in the younger age groups. Second, there is little evidence that decisions by patients are done in an environment where the actual numbers are conveyed to them in an understandable fashion. Part of the problem may be that most physicians are not aware of the numbers. Even if the direct monetary cost to the participant may approach zero, is it a good deal? If you have to put up with more than 500 false positives to find one cancer, and 95% of those cancers do not seem to behave malignantly anyway, is that an activity that most patients if well informed would buy in to?



The question is whether the present data on the effectiveness of mammography when presented to an informed consumer would convince individual women to spend their own money. We could make some estimates as to what the actual cost per person screened could be based upon a rough assumption of $100 per test and a biopsy rate of 1 woman biopsied by 10 screened. This means on average every woman will need to pay for 10 screens and one biopsy per decade. Whether this would end up being a needle or open biopsy or something even more involved such as sterotactic biopsy is an open question. Lets just assume a conservative $2000 cost. Add in another $1000 for total time travel, lost wages and productivity for a total cost of $4000. How many women would pay $4000 for the equivalent of a lottery ticket which to reduce their risk of death over the course of one decade by about 1 in 1000?

Welcome to the tragedy of the commons. All this discussion is irrelevant if services such as mammography are paid for by individual resources. The total cost of screening per woman screened is likely on the order of a few thousand dollars over the course of a decade, and represents pennies per day. That amount is hardly the stuff that insurance should pay for, being neither unpredictable or extremely costly.

This controversy is just one small piece of health care. Once you move to a system where resources are placed in a common pool and are allocated via some sort of consensus driven process, you have a mess. This latest controversy clearly shows that any attempt to base decisions on a scientific consensus are doomed. It involves people and the decision will be a political one. End of story. Now all we need to do is extrapolate this out to the entirety of health care decisions regarding allocation. If we can't unambiguously define whether mammograms are warranted as a health care right after all this investment of time and money, how are we going to deal with the defining the scope of the remaining 99.99999% of health care?

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