title: Estimating overdiagnosis in low-dose computed tomography screening for lung cancer: a cohort study.
abstract: BACKGROUND
  Lung cancer screening may detect cancer that will never become symptomatic (overdiagnosis), leading to overtreatment. Changes in size on sequential low-dose computed tomography (LDCT) screening, expressed as volume-doubling time (VDT), may help to distinguish aggressive cancer from cases that are unlikely to become symptomatic.
  
  
  OBJECTIVE
  To assess VDT for screening-detected lung cancer as an indicator of overdiagnosis.
  
  
  METHODS
  Retrospective estimation of the VDT of cancer detected in a prospective LDCT screening cohort.
  
  
  METHODS
  Nonrandomized, single-center screening study involving persons at high risk for lung cancer enrolled between 2004 and 2005 who received LDCT annually for 5 years.
  
  
  METHODS
  175 study patients diagnosed with primary lung cancer.
  
  
  METHODS
  VDT was measured on LDCT and classified as fast-growing (&lt;400 days), slow-growing (between 400 and 599 days), or indolent (≥600 days).
  
  
  RESULTS
  Fifty-five cases of cancer were diagnosed at baseline, and 120 were diagnosed subsequently. Of the latter group, 19 cases (15.8%) were new (not visible on previous scans) and fast-growing (median VDT, 52 days); 101 (84.2%) were progressive, including 70 (58.3%) fast-growing and 31 (25.8%) slow-growing (15.0%) or indolent (10.8%) cases. Lung cancer-specific mortality was significantly higher (9.2% per year) in patients with new compared with slow-growing or indolent (0.9% per year) cancer. Sixty percent of fast-growing progressive cancer and 45% of new cancer were stage I, for which survival was good.
  
  
  CONCLUSIONS
  This is a retrospective study. Volume-doubling time can only indicate overdiagnosis and was estimated for new cancer from 1 measurement (a diameter of 2 mm assumed the previous year).
  
  
  CONCLUSIONS
  Slow-growing or indolent cancer comprised approximately 25% of incident cases, many of which may have been overdiagnosed. To limit overtreatment in these cases, minimally invasive limited resection and nonsurgical treatments should be investigated.
  
  
  BACKGROUND
  Italian Association for Cancer Research.
authors.affiliation: Division of Thoracic Surgery, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy. giulia.veronesi@ieo.it
authors.forename: Giulia
authors.initials: G
authors.lastname: Veronesi
authors.forename: Patrick
authors.initials: P
authors.lastname: Maisonneuve
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellomi
authors.forename: Cristiano
authors.initials: C
authors.lastname: Rampinelli
authors.forename: Iara
authors.initials: I
authors.lastname: Durli
authors.forename: Raffaella
authors.initials: R
authors.lastname: Bertolotti
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spaggiari
mesh_terms: D055088:Early Detection of Cancer / Q000379:methods*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000473:pathology; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D064847:Multimodal Imaging; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden