title: Distribution of stage I lung cancer growth rates determined with serial volumetric CT measurements.
abstract: OBJECTIVE
  To retrospectively determine the distribution of stage I lung cancer growth rates with serial volumetric computed tomographic (CT) measurements.
  
  
  METHODS
  This study was institutional review board approved and HIPAA compliant. The informed consent requirement was waived. Patients (n = 149) with stage I lung cancer who underwent two pretreatment CT examinations 25 or more days apart were identified. At the first and last examinations, tumor perimeters were manually inscribed by using software tools and the cross-sectional area was calculated. To calculate tumor volume, the summed areas were multiplied by the section increment and a formula was applied to reduce partial volume effects. Doubling time (DT) was calculated by using the volume and interscanning interval. The percentages of tumors that would surpass volume increase thresholds of 5%-25% for detectable growth at different time intervals were calculated. Age at diagnosis was compared with the reciprocal of DT, time interval between CT examinations, and initial tumor volume by using Pearson correlation. P < .05 denoted statistical significance.
  
  
  RESULTS
  Lung cancer was stage IA in 99 patients and stage IB in 50. Median patient age was 72 years, and median interscanning interval was 130 days. Median tumor volumes were 3000 and 6213 mm3 at the first and last examinations, respectively. Median DT was 207 days; 21 tumors did not increase in volume between examinations. The interscanning interval required for 90% of growing tumors to surpass the growth threshold ranged from 8 weeks (5% threshold) to 37 weeks (25% threshold). Fifty-three percent of growing tumors would surpass the 25% threshold at 8 weeks, and 95% would surpass it at 1 year. Age at diagnosis was negatively correlated with growth rate (P = .047); there was no correlation between growth rate and either age at diagnosis or interscanning interval.
  
  
  CONCLUSIONS
  At serial volumetric CT measurements, there was wide variability in growth rates. Some biopsy-proved cancers decreased in volume between examinations.
authors.affiliation: Department of Radiology, Indiana University School of Medicine, 950 W Walnut St, Room E124, Indianapolis, IN 46202, USA. sajennin@iupui.edu
authors.forename: S Gregory
authors.initials: SG
authors.lastname: Jennings
authors.forename: Helen T
authors.initials: HT
authors.lastname: Winer-Muram
authors.forename: Mark
authors.initials: M
authors.lastname: Tann
authors.forename: Jun
authors.initials: J
authors.lastname: Ying
authors.forename: Ian
authors.initials: I
authors.lastname: Dowdeswell
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*