title: Variability of lung tumor measurements on repeat computed tomography scans taken within 15 minutes.
abstract: OBJECTIVE
  We use changes in tumor measurements to assess response and progression, both in routine care and as the primary objective of clinical trials. However, the variability of computed tomography (CT) -based tumor measurement has not been comprehensively evaluated. In this study, we assess the variability of lung tumor measurement using repeat CT scans performed within 15 minutes of each other and discuss the implications of this variability in a clinical context.
  
  
  METHODS
  Patients with non-small-cell lung cancer and a target lung lesion ≥ 1 cm consented to undergo two CT scans within a period of minutes. Three experienced radiologists measured the diameter of the target lesion on the two scans in a side-by-side fashion, and differences were compared.
  
  
  RESULTS
  Fifty-seven percent of changes exceeded 1 mm in magnitude, and 33% of changes exceeded 2 mm. Median increase and decrease in tumor measurements were +4.3% and -4.2%, respectively, and ranged from 23% shrinkage to 31% growth. Measurement changes were within ± 10% for 84% of measurements, whereas 3% met criteria for progression according to Response Evaluation Criteria in Solid Tumors (RECIST; ≥ 20% increase). Smaller lesions had greater variability of percent measurement change (P = .005).
  
  
  CONCLUSIONS
  Apparent changes in tumor diameter exceeding 1 to 2 mm are common on immediate reimaging. Increases and decreases less than 10% can be a result of the inherent variability of reimaging. Caution should be exercised in interpreting the significance of small changes in lesion size in the care of individual patients and in the interpretation of clinical trial results.
authors: Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065, USA.
authors: Geoffrey R
authors: GR
authors: Oxnard
authors: Binsheng
authors: B
authors: Zhao
authors: Camelia S
authors: CS
authors: Sima
authors: Michelle S
authors: MS
authors: Ginsberg
authors: Leonard P
authors: LP
authors: James
authors: Robert A
authors: RA
authors: Lefkowitz
authors: Pingzhen
authors: P
authors: Guo
authors: Mark G
authors: MG
authors: Kris
authors: Lawrence H
authors: LH
authors: Schwartz
authors: Gregory J
authors: GJ
authors: Riely
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008875:Middle Aged; D009367:Neoplasm Staging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*