title: Results of the two incidence screenings in the National Lung Screening Trial.
abstract: BACKGROUND
  The National Lung Screening Trial was conducted to determine whether three annual screenings (rounds T0, T1, and T2) with low-dose helical computed tomography (CT), as compared with chest radiography, could reduce mortality from lung cancer. We present detailed findings from the first two incidence screenings (rounds T1 and T2).
  
  
  METHODS
  We evaluated the rate of adherence of the participants to the screening protocol, the results of screening and downstream diagnostic tests, features of the lung-cancer cases, and first-line treatments, and we estimated the performance characteristics of both screening methods.
  
  
  RESULTS
  At the T1 and T2 rounds, positive screening results were observed in 27.9% and 16.8% of participants in the low-dose CT group and in 6.2% and 5.0% of participants in the radiography group, respectively. In the low-dose CT group, the sensitivity was 94.4%, the specificity was 72.6%, the positive predictive value was 2.4%, and the negative predictive value was 99.9% at T1; at T2, the positive predictive value increased to 5.2%. In the radiography group, the sensitivity was 59.6%, the specificity was 94.1%, the positive predictive value was 4.4%, and the negative predictive value was 99.8% at T1; both the sensitivity and the positive predictive value increased at T2. Among lung cancers of known stage, 87 (47.5%) were stage IA and 57 (31.1%) were stage III or IV in the low-dose CT group at T1; in the radiography group, 31 (23.5%) were stage IA and 78 (59.1%) were stage III or IV at T1. These differences in stage distribution between groups persisted at T2.
  
  
  CONCLUSIONS
  Low-dose CT was more sensitive in detecting early-stage lung cancers, but its measured positive predictive value was lower than that of radiography. As compared with radiography, the two annual incidence screenings with low-dose CT resulted in a decrease in the number of advanced-stage cancers diagnosed and an increase in the number of early-stage lung cancers diagnosed. (Funded by the National Cancer Institute; NLST ClinicalTrials.gov number, NCT00047385.).
authors.affiliation: Department of Radiological Sciences, David Geffen School of Medicine at the University of California at Los Angeles (UCLA), Los Angeles, CA 90024, USA. daberle@mednet.ucla.edu
authors.forename: Denise R
authors.initials: DR
authors.lastname: Aberle
authors.forename: Sarah
authors.initials: S
authors.lastname: DeMello
authors.forename: Christine D
authors.initials: CD
authors.lastname: Berg
authors.forename: William C
authors.initials: WC
authors.lastname: Black
authors.forename: Brenda
authors.initials: B
authors.lastname: Brewer
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Clingan
authors.forename: Fenghai
authors.initials: F
authors.lastname: Duan
authors.forename: Richard M
authors.initials: RM
authors.lastname: Fagerstrom
authors.forename: Ilana F
authors.initials: IF
authors.lastname: Gareen
authors.forename: Constantine A
authors.initials: CA
authors.lastname: Gatsonis
authors.forename: David S
authors.initials: DS
authors.lastname: Gierada
authors.forename: Amanda
authors.initials: A
authors.lastname: Jain
authors.forename: Gordon C
authors.initials: GC
authors.lastname: Jones
authors.forename: Irene
authors.initials: I
authors.lastname: Mahon
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Marcus
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Rathmell
authors.forename: JoRean
authors.initials: J
authors.lastname: Sicks
mesh_terms: D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008168:Lung / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D055613:Multiple Pulmonary Nodules / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D013902:Radiography, Thoracic; D012680:Sensitivity and Specificity; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D036542:Tomography, Spiral Computed