title: A comparative study on the risks of radiogenic second cancers and cardiac mortality in a set of pediatric medulloblastoma patients treated with photon or proton craniospinal irradiation.
abstract: OBJECTIVE
  To compare the risks of radiogenic second cancers and cardiac mortality in 17 pediatric medulloblastoma patients treated with passively scattered proton or field-in-field photon craniospinal irradiation (CSI).
  
  
  METHODS
  Standard of care photon or proton CSI treatment plans were created for all 17 patients in a commercial treatment planning system (TPS) (Eclipse version 8.9; Varian Medical Systems, Palo Alto, CA) and prescription dose was 23.4 or 23.4 Gy (RBE) to the age specific target volume at 1.8 Gy/fraction. The therapeutic doses from proton and photon CSI plans were estimated from TPS. Stray radiation doses were determined from Monte Carlo simulations for proton CSI and from measurements and TPS for photon CSI. The Biological Effects of Ionization Radiation VII report and a linear model based on childhood cancer survivor data were used for risk predictions of second cancer and cardiac mortality, respectively.
  
  
  RESULTS
  The ratios of lifetime attributable risk (RLARs) (proton/photon) ranged from 0.10 to 0.22 for second cancer incidence and ranged from 0.20 to 0.53 for second cancer mortality, respectively. The ratio of relative risk (RRR) (proton/photon) of cardiac mortality ranged from 0.12 to 0.24. The RLARs of both cancer incidence and mortality decreased with patient's age at exposure (e), while the RRRs of cardiac mortality increased with e. Girls had a significantly higher RLAR of cancer mortality than boys.
  
  
  CONCLUSIONS
  Passively scattered proton CSI provides superior predicted outcomes by conferring lower predicted risks of second cancer and cardiac mortality than field-in-field photon CSI for all medulloblastoma patients in a large clinically representative sample in the United States, but the magnitude of superiority depends strongly on the patients' anatomical development status.
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences at Houston, USA; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences at Houston, USA; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Howell
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences at Houston, USA; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA; Department of Radiation Oncology, American University of Beirut Medical Center, Lebanon.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Taddei
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences at Houston, USA; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA; Current address is: Scripps Proton Therapy Center, San Diego, CA, USA.
authors.forename: Annelise
authors.initials: A
authors.lastname: Giebeler
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, USA.
authors.forename: Anita
authors.initials: A
authors.lastname: Mahajan
authors.affiliation: The University of Texas Graduate School of Biomedical Sciences at Houston, USA; Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, USA; Medical Physics Program, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA. Electronic address: newhauser@lsu.edu.
authors.forename: Wayne D
authors.initials: WD
authors.lastname: Newhauser
mesh_terms: D000293:Adolescent; D002528:Cerebellar Neoplasms / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D061888:Craniospinal Irradiation / Q000009:adverse effects / Q000379:methods; D005260:Female; D006331:Heart Diseases / Q000209:etiology*; D006801:Humans; D008297:Male; D008527:Medulloblastoma / Q000532:radiotherapy*; D009010:Monte Carlo Method; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D016609:Neoplasms, Second Primary / Q000209:etiology*; D017785:Photons / Q000627:therapeutic use*; D061766:Proton Therapy; D011829:Radiation Dosage; D011839:Radiation, Ionizing; D012307:Risk Factors; D055815:Young Adult
keywords: Cardiac mortality; Craniospinal irradiation; Medulloblastoma; Proton therapy; Second cancer