TCS Daily

Colonoscopies: Up Yours!

By Arnold Kling - May 23, 2005 12:00 AM

"Keep in mind that colonoscopy is the most accurate way to screen for colon cancer because it enables doctors to detect colon polyps. Detection and removal of polyps is crucial to preventing colon cancer because we know that, in the vast majority of cases, this cancer begins in a polyp. While not all polyps will become cancerous, we currently have no way of predicting which polyps will eventually grow into cancerous ones. It is known that polyps tend to develop more rapidly in older people. Thus, for most people, colonoscopy screening is recommended starting at age 50."
-- Ronen Arai, MD

This essay will explain:


1. Why routine colonoscopies for people over 50 may not be cost effective

2. Why I am getting one, anyway

3. How this fits into the larger health care policy issues


The Cost-Benefit Calculation


The medical case for routine colonoscopy over the age of 50 is quite compelling. Colon cancer is one of the more common forms of cancer. Colonoscopy and polypectomy has been shown to be a very powerful prevention tool. Yet the cost-benefit calculation, based on the trade-off between longevity and expense, turns out to be quite close.


This article estimates that the lifetime risk of colon cancer is 6 percent. Colon cancer tends to kill relatively late, so that the increase in longevity from prevention is somewhat limited. If you were to prevent a colon cancer that otherwise might kill you at 78, your additional longevity could be anywhere from 0 (if something else kills you first) to 20 years. Let us assume an average increase in longevity of 5 years. Finally, my reading of this article is that routine colonoscopy would reduce the death rate from colon cancer, net of deaths caused by the procedure itself, by 60 percent.


We multiply these three numbers together: 5 years of additional longevity times 6 percent of the population times a 60 percent mortality reduction rate, or 5 times .06 times .6, equals .18, which is the average number of life-years saved per person by using routine colonoscopy.


What is the value of a life-year? Economist David Cutler, in his book on the costs and benefits of health care, argues for using $100,000, a figure which seems high to me, in part because it is almost three times per capita GDP. Using a more conservative figure of $30,000 for the value of a life-year, the dollar value of the benefits of routine colonoscopy is $30,000 times .18, or $5400.


If you obtain a colonoscopy every five years, starting at age 50, then between age 50 and age 75 you will have 6 colonoscopies. Dr. Arai, quoted above, gives a range of $500 to $1000 for the cost of a colonoscopy. If the cost is at the upper end of the range, then the cost of $6000 exceeds the benefits, which we calculated as $5400.


Why I am Getting One Anyway


There are three reasons the cost-benefit calculation comes out so close, in spite of the strong medical arguments for colonoscopy screening. One is that the procedure is relatively expensive. Another reason is that colon cancer kills so late. But the most important reason is that if 6 percent of the population is susceptible to colon cancer, then 94 percent of the population will get along just fine without any colonoscopy. The problem is, we do not know who they are!


From my personal perspective, I am willing to pay several thousand dollars in case I turn out to be one of the unlucky 6 percent. Using insurance jargon, I am risk averse, and I am willing to pay a premium to be protected against colon cancer. In addition to being risk averse, I also am particularly averse to the suffering that goes along with terminal cancer. Thus, I would pay an even larger premium to prevent cancer than to prevent a less painful or drawn-out cause of death.


What I am saying is that if cost-benefit calculation for colonoscopy makes it seem not worth while, then I think that the flaw is in cost-benefit calculation. That calculation fails to take into account reasonable aversion to risk and to suffering. Taking those factors into account, I endorse routine colonoscopy.


Implications for Health Care Policy


Paul Krugman and others keep harping on the fact that the United States spends more on health care than other industrial countries, yet our longevity statistics are no better. From the standpoint of that trade-off, colonoscopies are part of the problem.


According to an international statistical comparison using data from the late 1980's, the five-year survival rate for colon cancer in the United States was the highest of the nine countries studied. However, none of the countries had a survival rate less than 40 percent. The United States does a better job than other countries at preventing and treating colon cancer, but the difference in terms of average longevity in the population as a whole is almost certainly less than one-tenth of one life-year.


The benefits of colonoscopy are concentrated in a small segment of the population and are invisible in the aggregate statistics on longevity. The costs, however, are incurred every time the procedure is undertaken, and they are quite visible in our health care spending statistics.


Colonoscopy is an example of what I call activist medicine, which means the use of expensive specialists and technology when there is a low probability of affecting the outcome. I personally think that routine colonoscopy is worthwhile, and I can sympathize with others who agree. However, it may appear otherwise to those who are fixated on the trade-off between aggregate longevity and cost.


If the benefit-cost ratio for colonoscopy is problematic, then it is probably much worse for many other practices in activist medicine. I think it would help to have solid information on the effectiveness of all common medical practices. However, the estimated benefits ought to go beyond average longevity to accommodate aversion to risk and aversion to suffering.


In order to bring about constructive change, I believe that three things must take place.


1. We have to recognize the futility of scapegoating health insurers, drug companies, and other health care providers. It may be emotionally satisfying to denounce suppliers and accuse them of waste and profiteering. However, the reality is that the sharp rise in health care spending in the United States in the past few decades has been largely driven by activist medicine -- by the increased volume of health care services that we consume.


2. We ought to undertake more research about the effectiveness of medical practices, so that we have a better idea when activist medicine provides substantial benefits and when it fails to do so.


3. We need to find ways to encourage doctors and consumers to make sound, data-driven decisions about activist medicine. Unfortunately, third-party payments take away much of the incentive for doctors and consumers to weigh benefits and costs.



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