title: Final screening round of the NELSON lung cancer screening trial: the effect of a 2.5-year screening interval.
abstract: In the USA annual lung cancer screening is recommended. However, the optimal screening strategy (eg, screening interval, screening rounds) is unknown. This study provides results of the fourth screening round after a 2.5-year interval in the Dutch-Belgian Lung Cancer Screening trial (NELSON).
  
  
  
  Europe's largest, sufficiently powered randomised lung cancer screening trial was designed to determine whether low-dose CT screening reduces lung cancer mortality by ≥25% compared with no screening after 10 years of follow-up. The screening arm (n=7915) received screening at baseline, after 1 year, 2 years and 2.5 years. Performance of the NELSON screening strategy in the final fourth round was evaluated. Comparisons were made between lung cancers detected in the first three rounds, in the final round and during the 2.5-year interval.
  
  
  
  In round 4, 46 cancers were screen-detected and there were 28 interval cancers between the third and fourth screenings. Compared with the second round screening (1-year interval), in round 4 a higher proportion of stage IIIb/IV cancers (17.3% vs 6.8%, p=0.02) and higher proportions of squamous-cell, bronchoalveolar and small-cell carcinomas (p=0.001) were detected. Compared with a 2-year interval, the 2.5-year interval showed a higher non-significant stage distribution (stage IIIb/IV 17.3% vs 5.2%, p=0.10). Additionally, more interval cancers manifested in the 2.5-year interval than in the intervals of previous rounds (28 vs 5 and 28 vs 19).
  
  
  
  A 2.5-year interval reduced the effect of screening: the interval cancer rate was higher compared with the 1-year and 2-year intervals, and proportion of advanced disease stage in the final round was higher compared with the previous rounds.
  
  
  
  ISRCTN63545820.
authors.affiliation: Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Uraujh
authors.initials: U
authors.lastname: Yousaf-Khan
authors.affiliation: Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Carlijn
authors.initials: C
authors.lastname: van der Aalst
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Pim A
authors.initials: PA
authors.lastname: de Jong
authors.affiliation: Department of Radiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.|University of Groningen, University Medical Center Groningen, Center for Medical Imaging-North East Netherlands, Groningen, The Netherlands.
authors.forename: Marjolein
authors.initials: M
authors.lastname: Heuvelmans
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.|Department of Radiology, Kennemer Gasthuis, Haarlem, The Netherlands.
authors.forename: Ernst
authors.identifier: 0000-0002-1982-2763
authors.initials: E
authors.lastname: Scholten
authors.affiliation: Department of Pulmonary Medicine, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Lammers
authors.affiliation: Department of Radiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.|University of Groningen, University Medical Center Groningen, Center for Medical Imaging-North East Netherlands, Groningen, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: van Ooijen
authors.affiliation: Department of Pulmonary Medicine, University Hospital Gasthuisberg, Leuven, Belgium.
authors.forename: Kristiaan
authors.initials: K
authors.lastname: Nackaerts
authors.affiliation: Department of Pulmonary Medicine, Kennemer Gasthuis, Haarlem, The Netherlands.
authors.forename: Carla
authors.initials: C
authors.lastname: Weenink
authors.affiliation: Department of Pulmonary Diseases, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: Groen
authors.affiliation: Department of Radiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.|University of Groningen, University Medical Center Groningen, Center for Medical Imaging-North East Netherlands, Groningen, The Netherlands.
authors.forename: Rozemarijn
authors.initials: R
authors.lastname: Vliegenthart
authors.affiliation: Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ten Haaf
authors.affiliation: Department of Radiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.|University of Groningen, University Medical Center Groningen, Center for Medical Imaging-North East Netherlands, Groningen, The Netherlands.
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oudkerk
authors.affiliation: Department of Public Health, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: de Koning
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000556:secondary; D055088:Early Detection of Cancer / Q000379:methods*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D055752:Small Cell Lung Carcinoma / Q000000981:diagnostic imaging* / Q000556:secondary; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Clinical Epidemiology; Lung Cancer; Non-Small Cell Lung Cancer; Small Cell Lung Cancer; Tobacco and the lung