title: Early changes of parotid density and volume predict modifications at the end of therapy and intensity of acute xerostomia.
abstract: OBJECTIVE
  To quantitatively assess the predictive power of early variations of parotid gland volume and density on final changes at the end of therapy and, possibly, on acute xerostomia during IMRT for head-neck cancer.
  
  
  METHODS
  Data of 92 parotids (46 patients) were available. Kinetics of the changes during treatment were described by the daily rate of density (rΔρ) and volume (rΔvol) variation based on weekly diagnostic kVCT images. Correlation between early and final changes was investigated as well as the correlation with prospective toxicity data (CTCAEv3.0) collected weekly during treatment for 24/46 patients.
  
  
  RESULTS
  A higher rΔρ was observed during the first compared to last week of treatment (-0,50 vs -0,05HU, p-value = 0.0001). Based on early variations, a good estimation of the final changes may be obtained (Δρ: AUC = 0.82, p = 0.0001; Δvol: AUC = 0.77, p = 0.0001). Both early rΔρ and rΔvol predict a higher "mean" acute xerostomia score (≥ median value, 1.57; p-value = 0.01). Median early density rate changes for patients with mean xerostomia score ≥ / < 1.57 were -0.98 vs -0.22 HU/day respectively (p = 0.05).
  
  
  CONCLUSIONS
  Early density and volume variations accurately predict final changes of parotid glands. A higher longitudinally assessed score of acute xerostomia is well predicted by higher rΔρ and rΔvol in the first two weeks of treatment: best cut-off values were -0.50 HU/day and -380 mm(3)/day for rΔρ and rΔvol respectively. Further studies are necessary to definitively assess the potential of early density/volume changes in identifying more sensitive patients at higher risk of experiencing xerostomia.
authors.affiliation: Medical Physics, Ospedale San Raffaele Scientific Institute, Via Olgettina 60, 20132, Milano, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Belli
authors.forename: Elisa
authors.initials: E
authors.lastname: Scalco
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Sanguineti
authors.forename: Claudio
authors.initials: C
authors.lastname: Fiorino
authors.forename: Sara
authors.initials: S
authors.lastname: Broggi
authors.forename: Nicola
authors.initials: N
authors.lastname: Dinapoli
authors.forename: Francesco
authors.initials: F
authors.lastname: Ricchetti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.forename: Giovanna
authors.initials: G
authors.lastname: Rizzo
authors.forename: Giovanni Mauro
authors.initials: GM
authors.lastname: Cattaneo
mesh_terms: D015502:Absorptiometry, Photon; D000208:Acute Disease; D042241:Early Diagnosis; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D007558:Italy; D008297:Male; D009929:Organ Size / Q000528:radiation effects; D010306:Parotid Gland / Q000000981:diagnostic imaging* / Q000528:radiation effects; D011832:Radiation Injuries / Q000000981:diagnostic imaging* / Q000209:etiology*; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014481:United States; D014987:Xerostomia / Q000000981:diagnostic imaging* / Q000209:etiology*
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