For older Americans who are or used to be heavy smokers, annual CT screening for lung cancer appears to reduce mortality from the disease, according to a report published online in the New England Journal of Medicine.
The results from the initial round of screening in the National Lung Screening Trial show that over a 3-year period, annual low-dose helical CT detected significantly more early-stage lung cancers than conventional chest radiography did, said Dr. Timothy R. Church of the division of environmental health sciences, University of Minnesota School of Public Health, Minneapolis, and his associates in the NLST research group.
In the real-world clinical settings, "a reduction in mortality from lung cancer is achievable at U.S. screening centers that have staff experienced in chest CT," they added.
The findings were published online and simultaneously presented at the annual meeting of the American Thoracic Society.
For this first round of the study, 53,454 asymptomatic men and women aged 55-74 years participated. All had a history of at least 30 pack-years of smoking and were either current smokers or had quit within the preceding 15 years.
The study subjects were treated and followed at 33 sites across the country and were randomly assigned to undergo either low-dose helical CT (26,722 patients) or chest radiography (26,732 patients) to screen for lung cancer every year for 3 years. Eight of these subjects were found to have lung cancer before their first screening could be done and were excluded from the study.
The proportion of study subjects who had positive screening results was markedly higher with low-dose CT scanning (27.3%) than with radiography (9.2%). Lung cancer was diagnosed in 1.1% of the CT group, compared with 0.7% of the radiography group.
In the CT group, 92.5% of the patients who developed lung cancer had a positive screening result (a true-positive result) and 6.2% had a negative screening result (a false-negative result); the remaining subjects missed their scheduled screening visit.
In the radiography group, 71.6% of the patients who developed lung cancer had a true-positive screening result and 25.8% had a false-negative result; the remaining subjects missed their scheduled screening visit.
Thus, the sensitivity and specificity of lung CT were 93.8% and 73.4%, respectively, compared with 73.5% sensitivity and 91.3% specificity for radiography, Dr. Church and his colleagues said (N. Engl. J. Med. 2013 [doi:10.1056/NEJMoa1209120]).
"There were many more bronchioloalveolar carcinomas and adenocarcinomas in the low-dose CT group than in the radiography group (38 vs. 8 and 123 vs. 71, respectively), but the frequencies of other histologic features were similar in the two groups," the investigators said.
The difference between the two groups in the number of detected cancers was almost entirely accounted for by early, stage IA tumors, which were markedly more likely to be identified on CT screening. The rates of detection were fairly comparable between CT and radiography for all the more advanced malignancies.
The study was funded by the National Cancer Institute. No financial conflicts of interest were reported.