Radiologists Rap Study Linking CT Scans with Cancer

John Commins, for HealthLeaders Media , December 15, 2009

The American College of Radiology today challenged the validity of two studies published this week in the Archives of Internal Medicine that link the overuse of CT scans with thousands of new cancer diagnoses and deaths.

At the same time, ACR acknowledged that widespread CT scan use has resulted in increased radiation exposure for Americans, and called for greater oversight and vigilance to prevent needless overuse.

"No published studies show that radiation from imaging exams causes cancer," ACR said in media release. "The conclusions of the authors of the Archives' studies rely largely on data which equates radiation exposure and effects experienced by atomic bomb survivors in Japan to present day patients who receive computed tomography scans."

One of the AIM studies used claims data from Medicare, and commercial insurance databases, and estimated that there were 72 million CT scans performed in 2007, which resulted in 29,000 excess cancer diagnoses, and as many as 15,000 additional cancer deaths for that year.

"Presumably, as the number of CT scans increase from the 2007 rate, the number of excess cancers also will increase. In light of these data, physicians (and their patients) cannot be complacent about the hazards of radiation or we risk creating a public health time bomb," AIM wrote in an editorial supporting the studies.

However, ACR challenged the studies' assumptions. "The articles—after excluding patients with cancer or within five years of the end of life—assumed that those undergoing CT scanning have the same life expectancy as the general population. This is not accurate, so the estimates are undoubtedly high," ACR said. "Moreover, 25% of people in the United States die of cancer with a lifetime incidence of 40%, about 1.5 million new cancers per year. The 29,000 figure, if even close to accurate, is overall a very small risk versus the immediate, proven life-saving benefits of CT."

Rather than posing a medical menace, ACR said CT scans have been linked to greater life expectancy, declines in cancer mortality rates, and are generally less expensive than the invasive procedures that they replace.

ACR said it supports and recommends that imaging exams be performed only if there is a clear medical benefit that outweighs any associated risk. ACR added it supports the "as low as reasonably achievable" concept which urges providers to use the minimum level of radiation needed in imaging exams to achieve the necessary results.

John Commins is a senior editor with HealthLeaders Media.

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