title: Appearances of screen-detected versus symptomatic colorectal cancers at CT colonography.
abstract: OBJECTIVE
  The aim of this study was to compare the morphology, radiological stage, conspicuity, and computer-assisted detection (CAD) characteristics of colorectal cancers (CRC) detected by computed tomographic colonography (CTC) in screening and symptomatic populations.
  
  
  METHODS
  Two radiologists independently analyzed CTC images from 133 patients diagnosed with CRC in (a) two randomized trials of symptomatic patients (35 patients with 36 tumours) and (b) a screening program using fecal occult blood testing (FOBt; 98 patients with 100 tumours), measuring tumour length, volume, morphology, radiological stage, and subjective conspicuity. A commercial CAD package was applied to both datasets. We compared CTC characteristics between screening and symptomatic populations with multivariable regression.
  
  
  RESULTS
  Screen-detected CRC were significantly smaller (mean 3.0 vs 4.3 cm, p < 0.001), of lower volume (median 9.1 vs 23.2 cm3, p < 0.001) and more frequently polypoid (34/100, 34 % vs. 5/36, 13.9 %, p = 0.02) than symptomatic CRC. They were of earlier stage than symptomatic tumours (OR = 0.17, 95 %CI 0.07-0.41, p < 0.001), and were judged as significantly less conspicuous (mean conspicuity 54.1/100 vs. 72.8/100, p < 0.001). CAD detection was significantly lower for screen-detected (77.4 %; 95 %CI 67.9-84.7 %) than symptomatic CRC (96.9 %; 95 %CI 83.8-99.4 %, p = 0.02).
  
  
  CONCLUSIONS
  Screen-detected CRC are significantly smaller, more frequently polypoid, subjectively less conspicuous, and less likely to be identified by CAD than those in symptomatic patients.
  
  
  CONCLUSIONS
  • Screen-detected colorectal cancers (CRC) are significantly smaller than symptomatic CRC. • Screening cases are significantly less conspicuous to radiologists than symptomatic tumours. • Screen-detected CRC have different morphology compared to symptomatic tumours (more polypoid, fewer annular). • A commercial computer-aided detection (CAD) system was significantly less likely to note screen-detected CRC.
authors.affiliation: Centre for Medical Imaging, University College London, London, UK.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Plumb
authors.affiliation: Centre for Medical Imaging, University College London, London, UK.
authors.forename: Fiona
authors.initials: F
authors.lastname: Pathiraja
authors.affiliation: Public Health England, Fulwood House, Sheffield, UK.
authors.forename: Claire
authors.initials: C
authors.lastname: Nickerson
authors.affiliation: Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Katherine
authors.initials: K
authors.lastname: Wooldrage
authors.affiliation: Intestinal Imaging Centre, St Mark's Hospital, Harrow, UK.
authors.forename: David
authors.initials: D
authors.lastname: Burling
authors.affiliation: Centre for Medical Imaging, University College London, London, UK.
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Taylor
authors.affiliation: Department of Surgery and Cancer, Imperial College London, London, UK.
authors.forename: Wendy S
authors.initials: WS
authors.lastname: Atkin
authors.affiliation: Centre for Medical Imaging, University College London, London, UK. s.halligan@ucl.ac.uk.
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
mesh_terms: D000368:Aged; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D023881:Colonography, Computed Tomographic / Q000379:methods; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D009367:Neoplasm Staging; D015588:Observer Variation; D009780:Occult Blood; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: CT colonography; Colorectal neoplasms; Computer-assisted diagnosis; Mass screening; Occult blood