CT Lung Cancer Screening Benefits Outweigh Overdiagnosis Risks

December 9, 2013

Low-dose CT screening for lung cancer reduces lung cancer deaths, a benefit that outweighs the risk of overdiagnosis.

Computed tomography lung cancer screening significantly reduces lung cancer deaths in high-risk patients, according to a study published in JAMA Internal Medicine. People at high risk of developing lung cancer include those aged 55 to 79 who have a 30-pack year or greater history of smoking.

Overdiagnosis is frequently a concern with screening programs, however it is believed that the benefit significantly outweighs this risk, said the researchers from Duke University Medical Center in Durham, N.C.

Using data from 53,452 people who were at high for developing lung cancer, obtained from the National Lung Screening Trial (NLST), the researchers compared the use of low-dose CT (LDCT) with chest radiography (CXR). Overdiagnosis was calculated using two measures: the probability that lung cancer detected by screening with LDCT divided by all lung cancers detected by screening in the LDCT arm, and the number of cases that were considered to be over diagnosis relative to the number of people needed to screen to prevent one death from lung cancer.

The results showed that 1,089 lung cancers were reported in the LDCT arm and 969 in the CXR arm of the study. According to the researchers, among those in the LDCT arm, there was a 18.5 percent probability of overdiagnosis of any lung cancer, 22.5 percent for non-small cell lung cancer, and 78.9 percent for bronchioalveolar lung cancer. “The number of cases of overdiagnosis found among the 320 participants who would need to be screened in the NLST to prevent one death from lung cancer was 1.83,” wrote the authors.

“Physicians should certainly discuss the risk and benefits of CT lung cancer screening with patients - including that of over diagnosis. However, for high-risk patients, the group in which CT lung cancer screening is proposed, the lifesaving benefit outweighs the risks,” Paul Ellenbogen, MD, said in a release from the American College of Radiology. “It is now a matter of incorporating the available information - including this JAMA article - adjusting protocols to minimize those risks as we move forward.” Ellenbogen is the chair of the ACR Board of Chancellors.

To reduce the additional diagnostic testing and overdiagnosis, the lesion size threshold used to define a positive test can be increased from 4 mm used in the NIST trial to 6 mm, said Ella A. Kazerooni, MD, chair of the American College of Radiology Lung Cancer Screening Committee. This was shown by the I-ELCAP study earlier this year. “This JAMA study,” she said, “is another piece of information to help arrive at a screening program, available across the country, that saves lives and improves quality of life.”