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The Dangers of Incidental Tumor Findings from CT Scans

A new study shows that the risk of kidney removal surgery increases for Medicare beneficiaries living in a high-scanning region.

Meeri Kim, Contributor
Wednesday, January 10, 2018


In the mid-1990s, a patient came to see general internist H. Gilbert Welch with a hoarseness that refused to go away. Welch referred him to an otolaryngologist who found and removed a small vocal cord tumor, which fixed the problem. But sometime during the process, the patient also got a chest CT scan that unexpectedly uncovered a 5 centimeter-large mass on his kidney.

Two weeks later, to the patient’s shock, doctors recommended his kidney be removed -- a procedure with a 2.5 percent mortality rate at the time. The patient ultimately opted not to have the surgery, and the mass didn't grow or spread, as discovered after his death 10 years later. Welch never forgot this episode, and it made him wonder how many people had gotten treatment for a similar incidental but harmless finding.

“That case sensitized me to the problem of incidental detection, and in particular for renal cell carcinoma, where the incidence rate has more than doubled but the mortality rate has stayed totally flat,” said Welch, now a professor of medicine at Dartmouth College's Geisel School of Medicine. He believed that the higher incidence was due to doctors stumbling upon tumors during chest or abdominal CT scans.

Now, more than 20 years after he first saw the hoarse patient, Welch and his colleagues have published a study in JAMA Internal Medicine that quantifies the harms of incidental findings and advanced imaging overuse in medicine. They analyzed data from 15 million fee-for-service Medicare beneficiaries and found that those residing in high-scanning regions of the U.S. face a higher risk of kidney removal surgery. The paper appeared online on Dec. 26.

While the advent of CT revolutionized medicine, an unintended and harmful consequence of advanced imaging involves incidental findings. Doctors would order a diagnostic scan to identify the cause of clinical symptoms, such as the hoarseness in Welch's patient, and the imaging would discover an unrelated abnormality that then had to be acted upon.

“Most people think that the only harm of looking is radiation, but that’s not true,” said Welch. “The more consequential and common harm is that it starts a whole train of events that gets very hard to stop.”

The study used Medicare claims to measure the likelihood that an individual would have a CT scan during a 5-year period, as well as the likelihood they would have their kidney surgically removed. The data was grouped into 306 hospital referral regions, which represent regional health care markets and are population based. Kidney removal surgery, called nephrectomy, is commonly performed for kidney cancer diagnosed as a renal mass from CT.

Of all Medicare beneficiaries aged 65 to 85, almost half received either a chest or abdominal CT from January 2010 to December 2014. Hospital referral regions with a higher rate of CT scanning also had a higher nephrectomy risk, as Welch expected, particularly in those with more than 50,000 beneficiaries. For those who underwent the procedure, case-fatality rates were 2.1 percent at 30 days and 4.3 percent at 90 days.

“I think this paper is extremely important in that it helps quantify the harms of imaging overuse,” said Rebecca Smith-Bindman, a professor of radiology at the University of California, San Francisco School of Medicine who wrote a commentary on the paper. “Once a patient is diagnosed with a cancer and treated, it sounds like an incredible save -- but in fact, that’s not always the case.”

While radiation exposure and costs are well-known downsides to imaging overuse, incidental findings are too often seen as positive. Also, the problem of incidental findings goes beyond the kidney. Tumors of the liver, pituitary gland, thyroid gland, ovary, pancreas, and lungs have also been plagued by this issue.

One possible solution described by Welch is suppressing CT information from other parts of the body. Currently, a chest CT is able to capture a portion of the abdomen because of the curvature of the diaphragm. But it isn't difficult to suppress that information in order to lower the risk of incidental findings.

As a more immediate solution, both Welch and Smith-Bindman agree that widespread education about the harms of imaging overuse and a more conservative hand in terms of ordering CT scans could help the situation in the short term.

“Because there’s so much interest in imaging from both physicians and patients, a solution has to involve both groups as well,” said Smith-Bindman. “We need education about the harms of imaging, and both patients and doctors need to inform themselves in order to think more critically about when and why tests are appropriate.”