title: Methodology for adaptive and robust FDG-PET escalated dose painting by numbers in head and neck tumors.
abstract: OBJECTIVE
  To develop a methodology for using FDG PET/CT in adaptive dose painting by numbers (DPBN) in head and neck squamous cell carcinoma (HNSCC) patients. Issues related to noise in PET and treatment robustness against geometric errors are addressed.
  
  
  METHODS
  Five patients with locally advanced HNSCC scheduled for chemo-radiotherapy were imaged with FDG-PET/CT at baseline and 2-3 times during radiotherapy (RT). The GTVPET was segmented with a gradient-based method. A double median filter reduces the impact of noise in the PET uptake-to-dose conversion. Filtered FDG uptake values were linearly converted into a voxel-by-voxel prescription from 70 (median uptake) to 86 Gy (highest uptake). A PTVPET was obtained by applying a dilation of 2.5 mm to the entire prescription. Seven iso-uptake thresholds led to seven sub-levels compatible with the Tomotherapy HiArt(®) Treatment Planning System. Planning aimed to deliver a median dose of 56 Gy and 70 Gy in 35 fractions on the elective and therapeutic PTVs, respectively. Plan quality was assessed with quality volume histogram (QVH). At each time point, plans were generated with a total of 3-4 plans for each patient. Deformable image registration was used for automatic contour propagation and dose summation of the 3 or 4 treatment plans (MIMvista(®)).
  
  
  RESULTS
  GTVPET segmentations were performed successfully until week 2 of RT but failed in two patients at week 3. QVH analysis showed high conformity for all plans (mean VQ = 0.95 93%; mean VQ = 1.05 3.9%; mean QF 2.2%). Good OAR sparing was achieved while keeping high plan quality.
  
  
  CONCLUSIONS
  Our results show that adaptive FDG-PET-based escalated dose painting in patients with locally advanced HNSCC is feasible while respecting strict dose constraints to organs at risk. Clinical studies must be conducted to evaluate toxicities and tumor response of such a strategy.
authors.affiliation: a Department of Radiation Oncology , and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Differding
authors.affiliation: a Department of Radiation Oncology , and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Edmond
authors.initials: E
authors.lastname: Sterpin
authors.affiliation: a Department of Radiation Oncology , and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Janssens
authors.affiliation: b Department of Nuclear Medicine , and Center for Molecular Imaging, Radiotherapy and Oncology (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Universite catholique de Louvain, St-Luc University Hospital , Brussels , Belgium.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Hanin
authors.affiliation: a Department of Radiation Oncology , and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: John Aldo
authors.initials: JA
authors.lastname: Lee
authors.affiliation: a Department of Radiation Oncology , and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Institut de Recherche Expérimentale et Clinique (IREC), Université catholique de Louvain , Brussels , Belgium.
authors.forename: Vincent
authors.initials: V
authors.lastname: Grégoire
mesh_terms: D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000532:radiotherapy; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D006801:Humans; D021621:Imaging, Three-Dimensional; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18