title: Comparative dosimetry of three-phase adaptive and non-adaptive dose-painting IMRT for head-and-neck cancer.
abstract: OBJECTIVE
  The anatomical changes, which occur during the radiotherapy treatment for head-and-neck cancer, may compromise the effectiveness of the treatment. This study compares dosimetrical effects of adaptive (ART) and non-adaptive (RT) dose-painted radiotherapy.
  
  
  METHODS
  For 10 patients, three treatment phases were preceded by a planning PET/CT scan. In ART, phases II and III were planned using PET/CT2 and PET/CT3, respectively. In RT, phases II and III were planned on PET/CT1 and recalculated on PET/CT2 and PET/CT3. Deformable image co-registration was used to sum the dose distributions and to propagate regions-of-interest (ROIs) drawn on PET/CT1 to PET/CT2, PET/CT3 and a last-treatment-day CT-scan.
  
  
  RESULTS
  Re-adjusted dose-painting ART provided higher minimum and lower maximum doses in target ROIs in comparison to RT. On average, ART reduced the parotids' median dose and swallowing structures mean dose by 4.6-7.1% (p>0.05) and 3% (p=0.06), respectively. Dose differences for targets were from -1.6% to 6.6% and for organs-at-risk from -7.1% to 7.1%. Analysis of individual patient data showed large improvements of ROI dose/volume metrics by ART, reaching a 24.4% minimum-dose increase in the elective neck planning target volume and 21.1% median-dose decrease in swallowing structures.
  
  
  CONCLUSIONS
  Compared to RT, ART readjusts dose-painting, increases minimum and decreases maximum doses in target volumes and improves dose/volume metrics of organs-at-risk. The results favored the adaptive strategy, but also revealed considerable heterogeneity in patient-specific benefit. Reporting population-average effects underestimates the patient-specific benefits of ART.
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium. Electronic address: AnaMariaLuiza.Olteanu@uzgent.be.
authors.forename: Luiza A M
authors.initials: LA
authors.lastname: Olteanu
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Dieter
authors.initials: D
authors.lastname: Berwouts
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Indira
authors.initials: I
authors.lastname: Madani
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Werner
authors.initials: W
authors.lastname: De Gersem
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Vercauteren
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Fréderic
authors.initials: F
authors.lastname: Duprez
authors.affiliation: Department of Radiotherapy, Ghent University Hospital, Belgium.
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
mesh_terms: D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D064847:Multimodal Imaging / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Adaptive radiotherapy; Deformable image registration; Dose summation; Dose-painting; Head-and-neck cancer; IMRT