title: Sparing healthy tissue and increasing tumor dose using bayesian modeling of geometric uncertainties for planning target volume personalization.
abstract: OBJECTIVE
  To develop a mathematical tool that can update a patient's planning target volume (PTV) partway through a course of radiation therapy to more precisely target the tumor for the remainder of treatment and reduce dose to surrounding healthy tissue.
  
  
  METHODS
  Daily on-board imaging was used to collect large datasets of displacements for patients undergoing external beam radiation therapy for solid tumors. Bayesian statistical modeling of these geometric uncertainties was used to optimally trade off between displacement data collected from previously treated patients and the progressively accumulating data from a patient currently partway through treatment, to optimally predict future displacements for that patient. These predictions were used to update the PTV position and margin width for the remainder of treatment, such that the clinical target volume (CTV) was more precisely targeted.
  
  
  RESULTS
  Software simulation of dose to CTV and normal tissue for 2 real prostate displacement datasets consisting of 146 and 290 patients treated with a minimum of 30 fractions each showed that re-evaluating the PTV position and margin width after 8 treatment fractions reduced healthy tissue dose by 19% and 17%, respectively, while maintaining CTV dose.
  
  
  CONCLUSIONS
  Incorporating patient-specific displacement patterns from early in a course of treatment allows PTV adaptation for the remainder of treatment. This substantially reduces the dose to healthy tissues and thus can reduce radiation therapy-induced toxicities, improving patient outcomes.
authors.affiliation: Department of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne, Australia; Faculty of Health, Arts and Design, Swinburne University of Technology, Melbourne, Australia. Electronic address: Alan.Herschtal@petermac.org.
authors.forename: Alan
authors.initials: A
authors.lastname: Herschtal
authors.affiliation: Department of Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, Melbourne, Australia.
authors.forename: Luc
authors.initials: L
authors.lastname: Te Marvelde
authors.affiliation: School of Mathematical Sciences, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Australia.
authors.forename: Kerrie
authors.initials: K
authors.lastname: Mengersen
authors.affiliation: Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Australia; The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia.
authors.forename: Farshad
authors.initials: F
authors.lastname: Foroudi
authors.affiliation: Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, St. Leonards, Sydney, Australia; Northern Clinical School, University of Sydney, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Eade
authors.affiliation: Department of Radiation Therapy, Peter MacCallum Cancer Centre, Melbourne, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Pham
authors.affiliation: Northern Sydney Cancer Centre, Radiation Oncology Department, Royal North Shore Hospital, St. Leonards, Sydney, Australia.
authors.forename: Hannah
authors.initials: H
authors.lastname: Caine
authors.affiliation: The Sir Peter MacCallum Department of Oncology, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia; Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, Australia.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kron
mesh_terms: D059925:Anatomic Landmarks; D001499:Bayes Theorem; D057918:Fiducial Markers; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012984:Software; D047368:Tumor Burden; D035501:Uncertainty