Continuing Uncertainty About CT Screening for Lung Cancer

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Continuing Uncertainty About CT Screening for Lung Cancer

More cancers were detected, but screening affected neither the number of advanced cancers detected nor mortality.

In a recently published study of computed tomography screening for lung cancer, a large number of early-stage tumors were detected. However, the lack of a parallel control group made it impossible to determine whether survival was improved by early detection (Journal Watch Oct 25 2006). In this new study, 3246 asymptomatic current or former smokers from the U.S. and Italy received baseline and annual CT screening for a median of about 4 years. Results were compared with those expected in high-risk populations, based on validated prediction models.

There were 144 cases of lung cancer diagnosed with CT screening, compared with 45 cases expected, and 109 lung resections for cancer, compared with 11 expected. However, no significant difference was found between observed and expected numbers of advanced lung cancers detected (42 vs. 33) or deaths from lung cancer (38 vs. 39).

Comment: In this study of CT screening for lung cancer, cases of advanced lung cancer or death from lung cancer were no fewer than expected in this population. Although proponents of CT screening point to prolonged individual survival after detection, individual survival is not equivalent to improved population-based mortality rates, primarily because of lead-time bias (in which cancers are detected at an earlier stage, but eventual outcomes are the same). These results support neither CT screening for lung cancer nor a proposal that would require Medicare to pay for such screening. Both the study authors and the editorialists urge clinicians to await the results of ongoing randomized screening trials in the U.S. and Europe.

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine March 6, 2007

Citation(s):

Bach PB et al. Computed tomography screening and lung cancer outcomes. JAMA 2007 Mar 7; 297:953-61.

Medline abstract (Free)

Black WC and Baron JA. CT screening for lung cancer: Spiraling into confusion? JAMA 2007 Mar 7; 297:995-7.

Medline abstract (Free)

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