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1 in 5 CT Screenings for Lung Cancer Results in Overdiagnosis

 |  By cclark@healthleadersmedia.com  
   December 10, 2013

"Some of these individuals would never have known they had lung cancer, and never would have been treated for lung cancer… and would have died from other causes rather than from this disease," says one researcher.

Nearly one in five patients with a history of cigarette smoking who are diagnosed with lung cancer with recommended CT screening don't have a clinically significant disease and are overdiagnosed, but scientists don't yet have any way of knowing which ones.

"There's just no way to know that right now, but it is what we're working on," says Edward Patz, Jr. MD, lead author of a study in Monday's JAMA Internal Medicine and a professor of pathology and radiology at Duke University Medical Center. "But there are lots of groups working on biomarkers to find ways of making this distinction."

"What we're saying is that in the absence of screening, some of these individuals would never have known they had lung cancer, and never would have been treated for lung cancer, and never would have been labeled for lung cancer, and would have died from other causes rather than from this disease."

Currently, screening guidelines recommend CT testing for people with a 30-pack year history of cigarette smoking, or for former smokers who quit within the past 15 years. Those studies suggest that of those people diagnosed with lung cancer as a result of the CT, recommended treatment can result in a 20% reduction in lung cancer mortality compared with screening using chest radiography.

Patz and colleagues used data from the National Lung Screening Trial that compared low-dose CT with chest X-rays, which are considered to be as effective as no screening, performed on 53,452 people between the ages of 55 and 74 at high risk for lung cancer mainly because of their history of cigarette smoking.

What the researchers found was that the CT diagnosed 18.5% more people with lung cancer than did the chest X-ray.

Patz says that the research findings in no way suggest that patients at high risk should not undergo lung cancer screening. "But what we do say is that, for full disclosure, you need to let people know that there is this downside of screening." That's because for many of the people who are treated who didn't have clinically significant disease, "some will have inherent complications from their treatment," resulting in morbidity and mortality from the treatments and surgery, rather than the disease itself.

The study is consistent with other trends in cancer research, for example in prostate cancer, that "suggest we do need to reclassify what we've always considered to be cancer. We know now it's a broad disease, with lots of ways it can manifest. But the problem is really trying to separate out those whom you should treat and be aggressive with, versus those who have indolent disease, and right now, there's no way of knowing that."

An accompanying piece by Russell Harris, MD, and colleagues at the University of North Carolina, Chapel Hill, proposes a way to tally the types of harm to patients who undergo lung cancer screening, "to improve our thinking about the harms of screening."

They weighed resulting physical harm, such as exposure to radiation, the workup from a positive screening test, or endurance of treatment; psychological harm; financial harm, and missed opportunities to work or be with family and friends.

The researchers said their template or taxonomy is an effort "to help investigators, policy makers, clinicians and the public think more clearly and systematically about harms and to consider harms equally with benefits in decisions about screening. We do not assert that harms always outweigh benefits, only that it is always necessary to weigh the two."

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