title: Simple method to estimate mean heart dose from Hodgkin lymphoma radiation therapy according to simulation X-rays.
abstract: OBJECTIVE
  To describe a new method to estimate the mean heart dose for Hodgkin lymphoma patients treated several decades ago, using delineation of the heart on radiation therapy simulation X-rays. Mean heart dose is an important predictor for late cardiovascular complications after Hodgkin lymphoma (HL) treatment. For patients treated before the era of computed tomography (CT)-based radiotherapy planning, retrospective estimation of radiation dose to the heart can be labor intensive.
  
  
  METHODS
  Patients for whom cardiac radiation doses had previously been estimated by reconstruction of individual treatments on representative CT data sets were selected at random from a case-control study of 5-year Hodgkin lymphoma survivors (n=289). For 42 patients, cardiac contours were outlined on each patient's simulation X-ray by 4 different raters, and the mean heart dose was estimated as the percentage of the cardiac contour within the radiation field multiplied by the prescribed mediastinal dose and divided by a correction factor obtained by comparison with individual CT-based dosimetry.
  
  
  RESULTS
  According to the simulation X-ray method, the medians of the mean heart doses obtained from the cardiac contours outlined by the 4 raters were 30 Gy, 30 Gy, 31 Gy, and 31 Gy, respectively, following prescribed mediastinal doses of 25-42 Gy. The absolute-agreement intraclass correlation coefficient was 0.93 (95% confidence interval 0.85-0.97), indicating excellent agreement. Mean heart dose was 30.4 Gy with the simulation X-ray method, versus 30.2 Gy with the representative CT-based dosimetry, and the between-method absolute-agreement intraclass correlation coefficient was 0.87 (95% confidence interval 0.80-0.95), indicating good agreement between the two methods.
  
  
  CONCLUSIONS
  Estimating mean heart dose from radiation therapy simulation X-rays is reproducible and fast, takes individual anatomy into account, and yields results comparable to the labor-intensive representative CT-based method. This simpler method may produce a meaningful measure of mean heart dose for use in studies of late cardiac complications.
authors: Department of Psychosocial Research, Epidemiology, and Biostatistics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Frederika A
authors: FA
authors: van Nimwegen
authors: Clinical Trial Service Unit, University of Oxford, Oxford, United Kingdom; Oxford Cancer Centre, Oxford University Hospitals NHS Trust, Oxford, United Kingdom.
authors: David J
authors: DJ
authors: Cutter
authors: Department of Psychosocial Research, Epidemiology, and Biostatistics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Michael
authors: M
authors: Schaapveld
authors: Department of Radiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Annemarieke
authors: A
authors: Rutten
authors: Department of Psychosocial Research, Epidemiology, and Biostatistics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Karen
authors: K
authors: Kooijman
authors: Department of Radiation Oncology, Leiden University Medical Center, Leiden, The Netherlands.
authors: Augustinus D G
authors: AD
authors: Krol
authors: Department of Radiation Oncology, Erasmus MC Cancer Center, Rotterdam, The Netherlands.
authors: Cécile P M
authors: CP
authors: Janus
authors: Clinical Trial Service Unit, University of Oxford, Oxford, United Kingdom.
authors: Sarah C
authors: SC
authors: Darby
authors: Department of Psychosocial Research, Epidemiology, and Biostatistics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Flora E
authors: FE
authors: van Leeuwen
authors: Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. Electronic address: b.aleman@nki.nl.
authors: Berthe M P
authors: BM
authors: Aleman
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects*; D006689:Hodgkin Disease / Q000000981:diagnostic imaging / Q000401:mortality / Q000532:radiotherapy*; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D011829:Radiation Dosage; D011859:Radiography; D015203:Reproducibility of Results; D013154:Spleen / Q000000981:diagnostic imaging / Q000528:radiation effects; D017741:Survivors; D055815:Young Adult