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Do I Need 9 Lives Just to Get a Cat Scan?

Posted Feb 21 2011 10:35pm

Hans Thoma (1901)

Hans Thoma (1901)

Tonight’s post will be relatively brief, as I wish only to call attention to another post and a particularly disturbing number contained therein. The post was published over at The Health Care Blog by Robert Wachter, MD, a leading figure in the modern patient safety movement. It is entitled A Game-Changing Statistic: 1 in 250 .” It is. Or at least it should be. You should take a minute or two to read it– it’s provoking, and not in a good way.

The 1 in 250 refers to the odds of getting cancer from a single CT scan.

Wachter writes:

Last month, my colleague Rebecca Smith-Bindman , professor of radiology, epidemiology, and ob/gyn at UCSF and one of the nation’s experts in the risks of radiographs, gave Medical Grand Rounds at UCSF. Her talk was brimming with amazing statistics , but this is the one that took my breath away:

A 20-year old woman who gets an abdominal-pelvic CT scan (i.e., just about any young woman coming to the ED with belly pain) has a 1 in 250 chance of getting cancer from that single scan.

Did that fully register? One CAT scan, which until recently most of us ordered with no more restraint than we exhibit when asking the Starbucks barista for a tall latte, will cause cancer in one out of every 250 patients. Two-hundred fifty: that’s the number of students in my college Bio 101 class. Wow.

Wachter adds fuel to that disturbing fire and reports that his above mentioned colleague found both increased radiation dosage (66% greater than that which is the usually quoted dose) and wide variation in dosage among different scanners in 4 Bay area hospitals.

If the variation and increased dosage isn’t scary enough, perhaps this nugget from Wachter regarding the usual dose is:

The effects? Well, there’s the 1 in 250 number, but Wachter is kind enough to give us an aggregate estimate:

  • A 2004 study found that less than 50 percent of radiologists, and 9 percent of ER docs, were aware that CT scans could increase the subsequent risk of cancer.

Unfortunately, quite a few CT scans are done each year. And the number has risen dramatically over the last few decades–a more cynical man (or perhaps just a man who has read Atul Gawande and Adam Smith ) might think the increase in usage might bear some relationship to the high cost of purchase for a CT scan machine-Buy it and they will come. Wachter tells us that

Even if only one-fifth were unnecessary, with a 1 in 250 chance of getting cancer from a single scan, the odds are ugly– and at least in some cases, amount to a dire risk without any merit whatsoever. In other cases, we risk greatly for minimal gain–and, perhaps, most disturbingly, that risk is often called for by doctors and radiologists who are sans knowledge of the risk. Yes,  a 1 in 250 chance of getting cancer from a single scan–when you perform 72 million of them per year–should be a game changer.

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