title: Methods for estimating the site of origin of locoregional recurrence in head and neck squamous cell carcinoma.
abstract: OBJECTIVE
  Methods to estimate the likely origin of recurrences after radiation therapy for head and neck squamous cell carcinoma are compared.
  
  
  METHODS
  A total of 25 patients meeting the following inclusion criteria were randomly selected: curatively intended intensity-modulated radiotherapy planned on a positron emission tomography-computed tomography (PET/CT) scan during the period 2005-2009; squamous cell carcinoma in the oral cavity, pharynx or larynx; complete clinical response followed by locoregional recurrence; and a CT scan at recurrence before any salvage therapy. Exclusion criteria were previous cancer in the area, surgery prior to radiotherapy, or a synchronous cancer. Three methods of estimating focal points of recurrence origin and two volume overlap methods assigning the recurrences to the most central target volumes encompassing at least 50% or 95% of the recurrence volumes were tested. Treatment planning and recurrence scans were rigid and deformable co-registered in order to transfer focal points to the treatment planning scan. Double determinations of all volumes, points, and co-registrations were made.
  
  
  RESULTS
  The volume overlap methods assigned the recurrences to significantly more peripheral target volumes than focal methods (p < 0.0001 for all comparisons of 95% overlap vs. focal methods, p < 0.028 for all comparisons of 50% overlap vs. focal methods). Repeated registrations of the same point had higher reproducibility with deformable registration than with rigid registration (median distance 0.31 vs. 0.35 cm, p = 0.015). No significant differences were observed among the focal methods.
  
  
  CONCLUSIONS
  Significant differences between methods were found which may affect strategies to improve radiotherapy based on pattern of failure analyses.
authors.affiliation: Department of Radiation Oncology Section 3994, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark. anne.k.due@sol.dk
authors.forename: A K
authors.initials: AK
authors.lastname: Due
authors.forename: I R
authors.initials: IR
authors.lastname: Vogelius
authors.forename: M C
authors.initials: MC
authors.lastname: Aznar
authors.forename: S M
authors.initials: SM
authors.lastname: Bentzen
authors.forename: A K
authors.initials: AK
authors.lastname: Berthelsen
authors.forename: S S
authors.initials: SS
authors.lastname: Korreman
authors.forename: C A
authors.initials: CA
authors.lastname: Kristensen
authors.forename: L
authors.initials: L
authors.lastname: Specht
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D059248:Chemoradiotherapy; D003131:Combined Modality Therapy; D019583:Dose Fractionation, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D008297:Male; D009062:Mouth Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D064847:Multimodal Imaging; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D009382:Neoplasms, Unknown Primary / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D010039:Otorhinolaryngologic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D010610:Pharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D049268:Positron-Emission Tomography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016879:Salvage Therapy; D000077195:Squamous Cell Carcinoma of Head and Neck; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden