"Finding more cancer is not the answer"

Will new detection guidelines lead to overdiagnosis of breast cancer?


Lynn Harris
April 11, 2007 10:31PM (UTC)

Money: It's a major argument against the American Cancer Society's new recommendation that women at high risk of breast cancer receive MRIs along with their mammograms (reported here on Broadsheet). MRIs, in short, are expensive. "All right, ACS," one can almost hear women saying, "My PPO won't pay for that -- I assume you will?"

"Not surprisingly, many insurers don't want to pay," acknowledge Dartmouth physicians H. Gilbert Welch, Lisa Schwartz and Steven Woloshin in an editorial in Tuesday's Washington Post. "So the big battle seems destined to be about who will. You will soon hear advocates talking about legislation to ensure payment and accusing those who do not want to pay for the test of denying access to lifesaving services simply to save money.

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"This," they add, "is wrong."

The focus on cost is ill placed, they say, because the recent study that bolstered the ACS guidelines does not necessarily prove that MRIs themselves find more cancer in the first place. Rather, they wonder, isn't it possible that you simply find more cancer when you do more tests? And is that really necessary? What follows is an interesting elaboration on the other major argument against potentially unnecessary MRIs: overdiagnosis.

In an earlier study, the authors note, women received two types of mammograms, one standard, one digital. The latter found more cancer. "But if you look at the numbers carefully, you'll find another story," they write. "Of the 237 breast cancers found by screening, 51 percent were detected by both tests, and 27 percent by digital exam alone. But the remaining 22 percent were detected only by the standard mammogram! So if the goal is simply find more cancer, you'd want to have both tests. There is reason to wonder whether this finding has less to do with the difference between the two tests and more with just having two tests. Given what we know about how different radiologists can look at the same mammogram and see different things, all you need to do is have your standard mammogram read by two radiologists rather than one, and you will find yet more cancer."

But: Is the best test the one that finds the most cancer? No: It's the one that finds the right cancer -- the cancer most likely to kill people. (Sometimes "watchful waiting" is deemed wiser than treatment, which has risks of its own.)

If you really want to know how well MRIs work, they say, do this randomized trial: Give half the participants MRIs, half mammograms. Then count how many in each group die. Such research, while not the least grim, is "the only way out of what is beginning to appear to be a vicious cycle: more and more testing finding more and more cancer, with the assumption of benefit," they write. In general, early detection is "a strategy that turns many more people into patients. Its effect on how many people die is relatively small, at best."

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I don't know what I would want for myself if I knew I were, say, at high risk for breast cancer; I can understand the urge to say "find it all, fast, and do whatever it takes to get rid of it!" But I found this argument compelling, too. After all, I'd also want to know that whatever tests were offered me had themselves been thoroughly tested as well.


Lynn Harris

Award-winning journalist Lynn Harris is author of the comic novel "Death by Chick Lit" and co-creator of BreakupGirl.net. She also writes for the New York Times, Glamour, and many others.

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