title: Reducing posttreatment dysphagia: Support for the relationship between radiation dose to the pharyngeal constrictors and swallowing outcomes.
abstract: OBJECTIVE
  This study used prospective swallowing data to establish the following: (1) whether doses to the pharyngeal constrictor muscles (PCMs) were significantly associated with swallowing outcomes; and (2) a mean dose constraint to aim for in intensity modulated radiation therapy planning.
  
  
  METHODS
  The PCMs were contoured and radiation dose data obtained for 55 patients with head and neck cancer. Associations between radiation dose and percentage of pharyngeal residue, penetration-aspiration and activity limitation measured at 6 months posttreatment were analyzed. Pretreatment swallowing function, tumor site, T classification, and chemotherapy were accounted for in multivariate analyses.
  
  
  RESULTS
  On multivariate analysis, the percentage of pharyngeal residue was statistically significantly associated with the mean dose to the superior PCM (95% confidence interval [CI], 0.15-1.66; P = .02). Penetration-aspiration was associated with the mean dose to the superior, middle, and inferior PCMs (95% CI, 1.02-1.27; P = .003; 95% CI, 1.02-1.23; P = .003; 95% CI, 1.04-1.21; P = .003, respectively) and the mean dose to the total PCM (95% CI, 1.05-1.31; P = .001). Activity limitation was also associated with the mean dose to the superior, middle, and inferior PCMs (95% CI, 1.01-1.20; P = .02; 95% CI, 1.00-1.15; P =.04; 95% CI, 1.01-1.15; P = .02, respectively) and the mean dose to the total PCM (95% CI, 1.02-1.23; P = .01). On univariate analysis, all 3 swallowing measures were statistically significantly worse for patients who received a biologically equivalent mean dose of >60 Gy to the PCMs. This remained significant on multivariate analysis for both penetration-aspiration and activity limitation (95% CI, 2.05-58.2, P = .004 and 95% CI, 1.14-27.7, P = .03, respectively).
  
  
  CONCLUSIONS
  The radiation dose to the PCMs is significantly associated with swallowing dysfunction. Limiting the mean PCM dose to less than 60 Gy results in better swallowing outcomes.
authors.affiliation: Department of Speech Pathology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia. Electronic address: jacqui.frowen@petermac.org.
authors.forename: Jacqui
authors.initials: J
authors.lastname: Frowen
authors.affiliation: Department of Radiation Therapy Services, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Colin
authors.initials: C
authors.lastname: Hornby
authors.affiliation: Centre for Biostatistics and Clinical Trials, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Marnie
authors.initials: M
authors.lastname: Collins
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Sashendra
authors.initials: S
authors.lastname: Senthi
authors.affiliation: Department of Diagnostic Imaging, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia.
authors.forename: Robin
authors.initials: R
authors.lastname: Cassumbhoy
authors.affiliation: Division of Radiation Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia; Department of Pathology, University of Melbourne, Grattan St, Parkville, Victoria, Australia.
authors.forename: June
authors.initials: J
authors.lastname: Corry