title: Parotid gland shrinkage during IMRT predicts the time to Xerostomia resolution.
abstract: OBJECTIVE
  To assess the impact of mid-treatment parotid gland shrinkage on long term xerostomia during IMRT for oropharyngeal SCC.
  
  
  METHODS
  All patients treated with IMRT at a single Institution from November 2007 to June 2010 and undergoing weekly CT scans were selected. Parotid glands were contoured retrospectively on the mid treatment CT scan. For each parotid gland, the percent change relative to the planning volume was calculated and combined as weighted average. Patients were considered to be xerostomic if developed GR2+ dry mouth according to CTCAE v3.0. Predictors of the time to xerostomia resolution or downgrade to 1 were investigated at both uni- and multivariate analysis.
  
  
  RESULTS
  85 patients were selected. With a median follow up of 35.8 months (range: 2.4-62.6 months), the actuarial rate of xerostomia is 26.2% (SD: 5.3%) and 15.9% (SD: 5.3%) at 2 and 3 yrs, respectively. At multivariate analysis, mid-treatment shrink along with weighted average mean parotid dose at planning and body mass index are independent predictors of the time to xerostomia resolution. Patients were pooled in 4 groups based on median values of both mid-treatment shrink (cut-off: 19.6%) and mean WA parotid pl-D (cut-off: 35.7 Gy). Patients with a higher than median parotid dose at planning and who showed poor shrinkage at mid treatment are the ones with the outcome significantly worse (3-yr rate of xerostomia ≈ 50%) than the other three subgroups (3-yr rate of xerostomia ≈ 10%).
  
  
  CONCLUSIONS
  For a given planned dose, patients whose parotids significantly shrink during IMRT are less likely to be long-term supplemental fluids dependent.
authors.affiliation: Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA. gsangui1@gmail.com.|Department of Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, USA. gsangui1@gmail.com.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sanguineti
authors.affiliation: Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA. francesco.ricchetti@sacrocuore.it.|Department of Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, USA. francesco.ricchetti@sacrocuore.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Ricchetti
authors.affiliation: Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA. Binbin.Wu@qunet.georgetown.edu.|Department of Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, USA. Binbin.Wu@qunet.georgetown.edu.
authors.forename: Binbin
authors.initials: B
authors.lastname: Wu
authors.affiliation: Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA. tmcnutt@jhmi.edu.|Department of Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD, USA. tmcnutt@jhmi.edu.
authors.forename: Todd
authors.initials: T
authors.lastname: McNutt
authors.affiliation: Department of Medical Physics, Ospedale San Raffaele, Milan, Italy. fiorino.claudio@hsr.it.
authors.forename: Claudio
authors.initials: C
authors.lastname: Fiorino
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009959:Oropharyngeal Neoplasms / Q000532:radiotherapy*; D010306:Parotid Gland / Q000473:pathology* / Q000528:radiation effects; D011379:Prognosis; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013997:Time Factors; D014987:Xerostomia / Q000175:diagnosis*