title: Radiotherapy of nasopharyngeal cancer using Rapidarc: dosimetric study of military teaching hospital Mohamed V, Morocco.
abstract: BACKGROUND
  The aim of the present study is to assess efficacy and efficiency of Volumetric-modulated arc therapy (VMAT) technique in treatment of nasopharyngeal cancer in our institution and to report toxicity related to this technique.
  
  
  METHODS
  Between June 2013 and January 2015, thirty-two patients with non metastatic nasopharyngeal cancer were curatively treated using VMAT Rapidarc. Dose prescription was performed using two different schedules, it consisted of either simultaneous integrated boost or simultaneous modulated accelerated radiation therapy delivering 70 Gy in 35 fractions and 69.96 in 33 fractions respectively. The choice was leaved at the discretion of the treating physician. The optimization process was performed by Eclipse software version 10.0 (Varian Medical Systems), using PRO algorithm (Progressive resolutive optimisation) version 3. Data was collected from dose-volume histograms for both planning target volumes (PTV) and organs at risk (OAR). We calculated the homogeneity index and the conformity index as well as the number of monitor units MU and the treatment delivery time. We also reported acute and late toxicity related to radiation therapy.
  
  
  RESULTS
  For the PTV high risk (HR), intermediate risk (PTV IR) and low risk (LR) the D95% was 97.21 ± 1.5, 97.5 ± 3.3 and 97.10 ± 6.86 respectively. Whereas, The D5% was 104.6 ± 2.16, 103.8 ± 2.1 and 100.89 ± 7.26. The CI for PTV HR was 0.98 ± 0.02 and the HI was 0.08 ± 0.02. The mean treatment delivery time was 2.3 ± 0.2, and the mean MU number was 527.6 ± 131.4. Grade 4 toxicity was not reported in any case. Grade 3 xerostomia was observed in only 3(9.4%) patients and no patients developed grade 3 hearing loss.
  
  
  CONCLUSIONS
  Our results confirmed the abilities of VMAT to provide excellent coverage of target volumes while sparing OAR especially the nervous structures and salivary glands.
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.|Cadi Ayyad University, Marrakech, Morocco.
authors.forename: Issam
authors.initials: I
authors.lastname: Lalya
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco. elaminmarnouche@gmail.com.
authors.forename: El Amin
authors.initials: EA
authors.lastname: Marnouche
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Maghous
authors.initials: M
authors.lastname: Abdelhak
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Noha
authors.initials: N
authors.lastname: Zaghba
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Khalid
authors.initials: K
authors.lastname: Andaloussi
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Elmarjany
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Laila
authors.initials: L
authors.lastname: Baddouh
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Keltoum
authors.initials: K
authors.lastname: Dahmani
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Khalid
authors.initials: K
authors.lastname: Hadadi
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Hassan
authors.initials: H
authors.lastname: Sifat
authors.affiliation: Department of Radiotherapy, Mohamed V Military Hospital, Rabat, Morocco.
authors.forename: Hamid
authors.initials: H
authors.lastname: Mansouri
mesh_terms: D000328:Adult; D003872:Dermatitis / Q000209:etiology; D005260:Female; D034381:Hearing Loss / Q000209:etiology; D006772:Hospitals, Military; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D008875:Middle Aged; D009018:Morocco; D052016:Mucositis / Q000209:etiology; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014987:Xerostomia / Q000209:etiology
keywords: Intensity-modulated radiotherapy; Nasopharyngeal cancer; Volumetric-modulated arc therapy