title: Automatic Coronary Artery Calcium Scoring on Radiotherapy Planning CT Scans of Breast Cancer Patients: Reproducibility and Association with Traditional Cardiovascular Risk Factors.
abstract: OBJECTIVE
  Coronary artery calcium (CAC) is a strong and independent predictor of cardiovascular disease (CVD) risk. This study assesses reproducibility of automatic CAC scoring on radiotherapy planning computed tomography (CT) scans of breast cancer patients, and examines its association with traditional cardiovascular risk factors.
  
  
  METHODS
  This study included 561 breast cancer patients undergoing radiotherapy between 2013 and 2015. CAC was automatically scored with an algorithm using supervised pattern recognition, expressed as Agatston scores and categorized into five categories (0, 1-10, 11-100, 101-400, >400). Reproducibility between automatic and manual expert scoring was assessed in 79 patients with automatically determined CAC above zero and 84 randomly selected patients without automatically determined CAC. Interscan reproducibility of automatic scoring was assessed in 294 patients having received two scans (82% on the same day). Association between CAC and CVD risk factors was assessed in 36 patients with CAC scores >100, 72 randomly selected patients with scores 1-100, and 72 randomly selected patients without CAC. Reliability was assessed with linearly weighted kappa and agreement with proportional agreement.
  
  
  RESULTS
  134 out of 561 (24%) patients had a CAC score above zero. Reliability of CVD risk categorization between automatic and manual scoring was 0.80 (95% Confidence Interval (CI): 0.74-0.87), and slightly higher for scans with breath-hold. Agreement was 0.79 (95% CI: 0.72-0.85). Interscan reliability was 0.61 (95% CI: 0.50-0.72) with an agreement of 0.84 (95% CI: 0.80-0.89). Ten out of 36 (27.8%) patients with CAC scores above 100 did not have other cardiovascular risk factors.
  
  
  CONCLUSIONS
  Automatic CAC scoring on radiotherapy planning CT scans is a reliable method to assess CVD risk based on Agatston scores. One in four breast cancer patients planned for radiotherapy have elevated CAC score. One in three patients with high CAC scores don't have other CVD risk factors and wouldn't have been identified as high risk.
authors.affiliation: Department of Epidemiology, Julius Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Sofie A M
authors.initials: SA
authors.lastname: Gernaat
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Ivana
authors.initials: I
authors.lastname: Išgum
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Bob D
authors.initials: BD
authors.lastname: de Vos
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Richard A P
authors.initials: RA
authors.lastname: Takx
authors.affiliation: Department of Epidemiology, Julius Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Danny A
authors.initials: DA
authors.lastname: Young-Afat
authors.affiliation: Devision of Internal Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Noor
authors.initials: N
authors.lastname: Rijnberg
authors.affiliation: Department of Epidemiology, Julius Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Diederick E
authors.initials: DE
authors.lastname: Grobbee
authors.affiliation: Department of Epidemiology, Julius Center, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: van der Graaf
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 Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Tim
authors.initials: T
authors.lastname: Leiner
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Desiree H J
authors.initials: DH
authors.lastname: van den Bongard
authors.affiliation: Department of Radiation Oncology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pignol
authors.affiliation: Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
mesh_terms: D000368:Aged; D000465:Algorithms; D001331:Automation; D001943:Breast Neoplasms / Q000532:radiotherapy*; D002118:Calcium / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000378:metabolism*; D015331:Cohort Studies; D003331:Coronary Vessels / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010347:Patient Care Planning; D015203:Reproducibility of Results; D012307:Risk Factors; D014057:Tomography, X-Ray Computed
chemical_list: D002118:Calcium