title: Swallowing-sparing intensity-modulated radiotherapy for head and neck cancer patients: treatment planning optimization and clinical introduction.
abstract: OBJECTIVE
  To report on the potential benefits of swallowing-sparing intensity-modulated radiation therapy (SW-IMRT) in the first 100 SW-IMRT treated patients, as well as on the factors that influence the potential benefit of SW-IMRT relative to standard parotid sparing (ST)-IMRT.
  
  
  METHODS
  One hundred consecutive head and neck cancer patients, scheduled for primary radiotherapy, were included in this prospective cohort study. For each patient, ST-IMRT and SW-IMRT treatment plans were created. All patients were eventually treated with SW-IMRT. Objectives for SW-IMRT were identical to those with ST-IMRT, with additional objectives to spare the swallowing organs at risk (SWOARs). After 20 patients, interim results were evaluated by a multidisciplinary committee.
  
  
  RESULTS
  The mean gain of SW-IMRT relative to ST-IMRT in the first 20 patients was less than expected based on our previous planning comparative study. A critical review of all plans revealed that the results with SW-IMRT could be improved by: (1) gaining experience and attempting to reduce SWOAR dose as much as possible; (2) accepting a moderate shift of dose to unspecified tissues; (3) maximizing SWOAR sparing while keeping PTV coverage exactly according to protocol. In the additional 80 patients, the mean dose to the various SWOARs was further reduced significantly compared to ST-IMRT. Dose reductions with SW-IMRT were largest for patients who received neck irradiation, had a tumour located in the larynx, oropharynx, nasopharynx or oral cavity, and had <75% overlap between SWOARs and PTVs. The mean absolute reduction in predicted physician-rated RTOG grade 2-4 swallowing dysfunction for patients numbered 21-100 was 6.1%, ranging from 0.0% to 17.2%.
  
  
  CONCLUSIONS
  The benefit of SW-IMRT depends significantly on neck radiotherapy, tumour site and the amount of overlap between SWOARs and PTVs. Optimal clinical introduction requires a detailed evaluation and comparison between the standard (ST-IMRT) and new technique (SW-IMRT) in order to fully exploit the potential benefits.
authors.affiliation: Department of Radiation Oncology, University of Groningen, University Medical Center Groningen, The Netherlands. h.p.van.der.laan@umcg.nl
authors.forename: Hans Paul
authors.initials: HP
authors.lastname: van der Laan
authors.forename: Agata
authors.initials: A
authors.lastname: Gawryszuk
authors.forename: Miranda E M C
authors.initials: ME
authors.lastname: Christianen
authors.forename: Roel J H M
authors.initials: RJ
authors.lastname: Steenbakkers
authors.forename: Erik W
authors.initials: EW
authors.lastname: Korevaar
authors.forename: Olga
authors.initials: O
authors.lastname: Chouvalova
authors.forename: Kim
authors.initials: K
authors.lastname: Wopken
authors.forename: Hendrik P
authors.initials: HP
authors.lastname: Bijl
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Langendijk
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003679:Deglutition / Q000528:radiation effects*; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D010306:Parotid Gland / Q000528:radiation effects; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
keywords: Clinical implementation; Head and neck cancer; IMRT; Normal tissue complication probability; Swallowing dysfunction