title: Brain-sparing methods for IMRT of head and neck cancer.
abstract: OBJECTIVE
  Radical radiotherapy for head and neck cancer (HNC) may deliver significant doses to brain structures. There is evidence that this may cause a decline in neurocognitive function (NCF). Radiation dose to the medial temporal lobes, and particularly to the hippocampi, seems to be critical in determining NCF outcomes. We evaluated the feasibility of two alternative intensity-modulated radiotherapy (IMRT) techniques to generate hippocampus- and brain-sparing HNC treatment plans to preserve NCF.
  
  
  METHODS
  A planning study was undertaken for ten patients with HNC whose planning target volume (PTV) included the nasopharynx. Patients had been previously treated using standard (chemo)-IMRT techniques. Bilateral hippocampi were delineated according to the RTOG atlas, on T1w MRI co-registered to the RT planning CT. Hippocampus-sparing plans (HSRT), and whole-brain/hippocampus-sparing fixed-field non-coplanar IMRT (BSRT) plans, were generated. DVHs and dose difference maps were used to compare plans. NTCP calculations for NCF impairment, based on hippocampal dosimetry, were performed for all plans.
  
  
  RESULTS
  Significant reductions in hippocampal doses relative to standard plans were achieved in eight of ten cases for both HSRT and BSRT. EQD2 D40% to bilateral hippocampi was significantly reduced from a mean of 23.5 Gy (range 14.5-35.0) in the standard plans to a mean of 8.6 Gy (4.2-24.7) for HSRT (p = 0.001) and a mean of 9.0 Gy (4.3-17.3) for BSRT (p < 0.001). Both HSRT and BSRT resulted in a significant reduction in doses to the whole brain, brain stem, and cerebellum.
  
  
  CONCLUSIONS
  We demonstrate that IMRT plans for HNC involving the nasopharynx can be successfully optimised to significantly reduce dose to the bilateral hippocampi and whole brain. The magnitude of the achievable dose reductions results in significant reductions in the probability of radiation-induced NCF decline. These results could readily be translated into a future clinical trial.
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Alex
authors.initials: A
authors.lastname: Dunlop
authors.affiliation: The Royal Marsden Hospital, London, United Kingdom; The Institute of Cancer Research, London, United Kingdom.
authors.forename: Liam
authors.initials: L
authors.lastname: Welsh
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Dualta
authors.initials: D
authors.lastname: McQuaid
authors.affiliation: The Institute of Cancer Research, London, United Kingdom.
authors.forename: Jamie
authors.initials: J
authors.lastname: Dean
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Sarah
authors.initials: S
authors.lastname: Gulliford
authors.affiliation: Joint Department of Physics, Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Vibeke
authors.initials: V
authors.lastname: Hansen
authors.affiliation: The Royal Marsden Hospital, London, United Kingdom; The Institute of Cancer Research, London, United Kingdom.
authors.forename: Shreerang
authors.initials: S
authors.lastname: Bhide
authors.affiliation: The Royal Marsden Hospital, London, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Nutting
authors.affiliation: The Royal Marsden Hospital, London, United Kingdom; The Institute of Cancer Research, London, United Kingdom.
authors.forename: Kevin
authors.initials: K
authors.lastname: Harrington
authors.affiliation: The Royal Marsden Hospital, London, United Kingdom.
authors.forename: Kate
authors.initials: K
authors.lastname: Newbold
mesh_terms: D000328:Adult; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006624:Hippocampus; D006801:Humans; D008297:Male; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods*; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013702:Temporal Lobe