title: Parotid gland volumetric changes during intensity-modulated radiotherapy in head and neck cancer.
abstract: OBJECTIVE
  To evaluate volumetric changes of parotid glands (PGs) during intensity-modulated radiotherapy (IMRT) in head and neck cancer patients.
  
  
  METHODS
  During IMRT all patients underwent kilovolt cone-beam CT (CBCT) scans to verify the set-up positioning in a protocol study. On each CBCT scan, the PGs were retrospectively contoured and evaluated with a dose-volume histogram.
  
  
  RESULTS
  From February to June 2011, 10 patients were enrolled. 140 CBCT scans were registered (280 PGs): for each patient, a median of 14 CBCT scans were performed (range 14-16). At the start of radiation, the average volume for ipsilateral PGs (iPGs) was 18.77 ml (range 12.9-31.2 ml), whereas for contralateral PGs (cPGs) it was 16.63 ml (range 8.3-28.7 ml). At the last CBCT scan, the average volume loss was 43.5% and 44.0% for the iPG and cPG, respectively. When we analysed the percentage of volume loss, we observed that the volume decreased by linear regression (r(2)=0.92 for iPG; r(2)=0.91 for cPG), with an average volume loss rate of 1.5% per day for both PGs. During the third week of treatment the volume of both PGs reduced by 24-30%.
  
  
  CONCLUSIONS
  Our data show that, during IMRT, the shrinkage of PGs should be taken into account. A replan could be indicated in the third week of radiotherapy.
authors.affiliation: Department of Radiation Oncology, IRCCS/CROB, Rionero in Vulture, Italy. albafiorentino@hotmail.it
authors.forename: A
authors.initials: A
authors.lastname: Fiorentino
authors.forename: R
authors.initials: R
authors.lastname: Caivano
authors.forename: V
authors.initials: V
authors.lastname: Metallo
authors.forename: C
authors.initials: C
authors.lastname: Chiumento
authors.forename: M
authors.initials: M
authors.lastname: Cozzolino
authors.forename: G
authors.initials: G
authors.lastname: Califano
authors.forename: S
authors.initials: S
authors.lastname: Clemente
authors.forename: P
authors.initials: P
authors.lastname: Pedicini
authors.forename: V
authors.initials: V
authors.lastname: Fusco
mesh_terms: D000328:Adult; D000368:Aged; D054893:Cone-Beam Computed Tomography; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D059351:Organ Sparing Treatments / Q000379:methods; D010306:Parotid Gland / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects*; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies