title: Impact of head and neck cancer adaptive radiotherapy to spare the parotid glands and decrease the risk of xerostomia.
abstract: BACKGROUND
  Large anatomical variations occur during the course of intensity-modulated radiation therapy (IMRT) for locally advanced head and neck cancer (LAHNC). The risks are therefore a parotid glands (PG) overdose and a xerostomia increase. The purposes of the study were to estimate: - the PG overdose and the xerostomia risk increase during a "standard" IMRT (IMRTstd); - the benefits of an adaptive IMRT (ART) with weekly replanning to spare the PGs and limit the risk of xerostomia.
  
  
  METHODS
  Fifteen patients received radical IMRT (70 Gy) for LAHNC. Weekly CTs were used to estimate the dose distributions delivered during the treatment, corresponding either to the initial planning (IMRTstd) or to weekly replanning (ART). PGs dose were recalculated at the fraction, from the weekly CTs. PG cumulated doses were then estimated using deformable image registration. The following PG doses were compared: pre-treatment planned dose, per-treatment IMRTstd and ART. The corresponding estimated risks of xerostomia were also compared. Correlations between anatomical markers and dose differences were searched.
  
  
  RESULTS
  Compared to the initial planning, a PG overdose was observed during IMRTstd for 59% of the PGs, with an average increase of 3.7 Gy (10.0 Gy maximum) for the mean dose, and of 8.2% (23.9% maximum) for the risk of xerostomia. Compared to the initial planning, weekly replanning reduced the PG mean dose for all the patients (p<0.05). In the overirradiated PG group, weekly replanning reduced the mean dose by 5.1 Gy (12.2 Gy maximum) and the absolute risk of xerostomia by 11% (p<0.01) (30% maximum). The PG overdose and the dosimetric benefit of replanning increased with the tumor shrinkage and the neck thickness reduction (p<0.001).
  
  
  CONCLUSIONS
  During the course of LAHNC IMRT, around 60% of the PGs are overdosed of 4 Gy. Weekly replanning decreased the PG mean dose by 5 Gy, and therefore by 11% the xerostomia risk.
authors.affiliation: Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France. j.castelli@rennes.unicancer.fr.|Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. j.castelli@rennes.unicancer.fr.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. j.castelli@rennes.unicancer.fr.
authors.forename: Joel
authors.initials: J
authors.lastname: Castelli
authors.affiliation: Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. antoine.simon@univ-rennes1.fr.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. antoine.simon@univ-rennes1.fr.
authors.forename: Antoine
authors.initials: A
authors.lastname: Simon
authors.affiliation: Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France. g.louvel@rennes.unicancer.fr.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Louvel
authors.affiliation: Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France. o.henry@rennes.unicancer.fr.
authors.forename: Olivier
authors.initials: O
authors.lastname: Henry
authors.affiliation: Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France. e.chajon@rennes.unicancer.fr.
authors.forename: Enrique
authors.initials: E
authors.lastname: Chajon
authors.affiliation: Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. mohamed.hatem.nassef@gmail.com.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. mohamed.hatem.nassef@gmail.com.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Nassef
authors.affiliation: Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. pascal.haigron@univ-rennes1.fr.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. pascal.haigron@univ-rennes1.fr.
authors.forename: Pascal
authors.initials: P
authors.lastname: Haigron
authors.affiliation: Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. guillaume.cazoulat@gmail.com.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. guillaume.cazoulat@gmail.com.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Cazoulat
authors.affiliation: Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. jdospina@gmail.com.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. jdospina@gmail.com.
authors.forename: Juan David
authors.initials: JD
authors.lastname: Ospina
authors.affiliation: CHU Pontchaillou, Rennes, F-35000, France. franck.jegoux@chu-rennes.fr.
authors.forename: Franck
authors.initials: F
authors.lastname: Jegoux
authors.affiliation: Centre Antoine Lacassagne, Nice, F-06100, France. Karine.BENEZERY@nice.unicancer.fr.
authors.forename: Karen
authors.initials: K
authors.lastname: Benezery
authors.affiliation: Department of Radiotherapy, Centre Eugene Marquis, Avenue de la bataille Flandre Dunkerque, F-35000, Rennes, France. r.de-crevoisier@rennes.unicancer.fr.|Rennes University 1, LTSI, Campus de Beaulieu, Rennes, F-35000, France. r.de-crevoisier@rennes.unicancer.fr.|INSERM, U1099, Campus de Beaulieu, Rennes, F-35000, France. r.de-crevoisier@rennes.unicancer.fr.
authors.forename: Renaud
authors.initials: R
authors.lastname: de Crevoisier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments; D010306:Parotid Gland; D011379:Prognosis; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014987:Xerostomia / Q000517:prevention & control*