A CT scan for kidney cancer? It may depend on where you live.

By | November 8, 2018

About one in fifty people reading this essay will be diagnosed with kidney cancer at some time in their life. In fact, one out of one people writing this essay has already been diagnosed with kidney cancer. (I had a small tumor removed from my left kidney not long after I turned 50.) But how many people diagnosed with kidney cancer have been overdiagnosed with the condition? And what does moving to Florida have to do with your chance of being diagnosed with kidney cancer?

Let’s start with some facts about kidney cancer. The number of people being diagnosed with kidney cancer is rising dramatically in the United States. Just between 2001 and 2010, the rate of such diagnoses grew almost 20%. Some of that increase is due to the aging of the American population, and some to the increased rate of obesity. But much of it results from the increasing number of people receiving CT scans in the United States, for one reason or another, with those scans revealing suspicious growth in their kidneys.

The use of CT imaging has grown dramatically in recent years, especially in some parts of the country. According to research out of Dartmouth, half of Medicare enrollees in Michigan received a CT scan of either their chest or abdomen between the beginning of 2010 and the end of 2014. That compares to around a third of people in Iowa over the same time period. Here’s a picture of how common CT scans are in different parts of the country, with darker ones (Florida!) having higher rates of such scans:

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When people get CT scans, doctors find abnormalities. Some of those abnormalities are serious problems that demand rapid medical attention. But some are incidental findings –“incidentalomas”– that don’t necessarily portend anything dire.

My kidney cancer was probably one of those incidentalomas. I had a scan of my abdomen to evaluate an unrelated medical problem. The scan revealed a 1 cm growth in my left kidney. I probably could have had the growth followed, to see if it just hung out there doing nothing, or to see whether it even shrank over time. Instead, I had it removed. Which is what lots of people do in that circumstance. Psychologically speaking, it is really hard to receive a diagnosis of kidney cancer and decide to do nothing to treat the cancer, even though there is little evidence that treating 1 cm kidney mass does any good.

As a result of all this diagnostic imaging, the number of people diagnosed and treated for kidney cancer has gone up significantly. If removing all these small cancers was curing people of life-threatening illnesses, you would expect the death rate to go down. But the death rate from kidney cancer hasn’t budged. Here is a picture that finding:

If all this early detection was good for people, then you’d expect death rates from kidney cancer to drop. The fact that they have remained steady suggests that most of those additional cancers removed … didn’t need to be removed. That is what medical experts mean by overdiagnosis. If you treat a medical condition that, if left alone, would not have harmed that person, then that diagnosis is an overdiagnosis.

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If you live in Florida and want to avoid an overdiagnosis of kidney cancer, you could move to Iowa. Or you could let your doctors know you want them to think twice — maybe three times — before ordering an unnecessary CT scan or before treating an incidental “diagnosis.”

Peter Ubel is a physician and behavioral scientist who blogs at his self-titled site, Peter Ubel and can be reached on Twitter @PeterUbel. He is the author of Critical Decisions: How You and Your Doctor Can Make the Right Medical Choices Together. This article originally appeared in Forbes.

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