Low-dose CT screening of adults at high risk for lung cancer was three times better than radiography at detecting early, more treatable malignancies in the National Lung Screening Trial, according to a report published online Sept. 4 in the New England Journal of Medicine.
The initial findings from the NLST showed that low-dose CT (LDCT) lung screening reduced lung-cancer mortality by 20%, relative to radiographic screening. The investigators now report more detailed findings from the first two rounds of screening, which show that this decrease in lung-cancer mortality "was coupled with a shift to detection of earlier-stage non-small-cell lung cancers," which are potentially curable, said Dr. Denise R. Aberle of the department of radiological sciences, University of California, Los Angeles, and her associates.
In the NLST, 53,454 adults at high risk for lung cancer were randomly assigned to undergo three annual screenings using either LDCT or radiography at 33 medical centers across the country. The screening took place between August 2002 and September 2007.
At the first round of screening, the sensitivity of LDCT was 94.4%, the specificity was 72.6%, the positive predictive value was 2.4%, and the negative predictive value was 99.9%. In comparison, the sensitivity of radiography was 59.6%, the specificity was 94.1%, the positive predictive value was 4.4%, and the negative predictive value was 99.8%.
At the second round of screening, LDCT’s sensitivity was 93%, specificity was 83.9%, positive predictive value was 5.2%, and negative predictive value was 99.9%. In comparison, radiography’s sensitivity was 63.9%, specificity was 95.3%, positive predictive value was 6.7%, and negative predictive value was 99.8%.
During the first round of screening, nearly half (47.5%) of the staged cancers detected on LDCT were stage IA, compared with only 23.5% of those detected on radiography. In contrast, only 31.1% of the staged cancers detected on LDCT were advanced stage III or IV cancers, compared with 59.1% of those detected on radiography.
This discrepancy in the distribution of early- vs. late-stage cancers persisted during the second round of screening, Dr. Aberle and her associates reported (N. Engl. J. Med. 2013 Sept. 4 [doi: 10.1056/NEJMoa1208962]).
In the future, "the performance characteristics of LDCT may be enhanced by determining the most appropriate risk cohort, refining both algorithms for interpreting the results of screening and definitions of positive findings, and determining the appropriate duration and timing of screening," they added.
The NLST was funded by the National Cancer Institute. Dr. Aberle reported no potential financial conflicts of interest; one of her associates reported ties to Endocyte, Frontier Science, and other companies.