title: Intensity-modulated radiotherapy for nasopharyngeal carcinoma: improvement of the therapeutic ratio with helical tomotherapy vs segmental multileaf collimator-based techniques.
abstract: OBJECTIVE
  The aim of the study was to compare differences in dosimetric, clinical and quality-of-life end points among patients treated with helical tomotherapy (HT) and segmental multileaf collimator (SMLC)-based intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma.
  
  
  METHODS
  From June 2005 to August 2009, 30 consecutive patients were treated with IMRT for nasopharyngeal carcinoma to a dose of 70 Gy. 14 patients (47%) were treated using HT and 16 (53%) were treated using SMLC-based IMRT. 28 patients (93%) received concurrent chemotherapy. The patients were evenly balanced between the two radiotherapy groups with respect to clinical and pathological characteristics. Median follow-up was 30 months (range, 6-62 months).
  
  
  RESULTS
  The 2-year estimates of overall survival, local-regional control and progression-free survival were 81%, 87% and 82%, respectively. There were no significant differences in any of these end points with respect to IMRT technique (p>0.05 for all). Dosimetric analysis revealed that patients treated by HT had significantly improved salivary sparing with respect to mean dose (27.3 vs 34.1 Gy, p=0.03) and volume receiving greater than or equal to 30 Gy (31.7% vs 47.3%, p=0.01) to the contralateral (spared) parotid gland. The incidence of Grade 3+ late xerostomia was 13 and 7% among patients treated with SMLC-based IMRT and HT, respectively (p=0.62). The corresponding proportion of patients who subjectively reported "too little" or "no" saliva at final follow-up was 38% and 7%, respectively (p=0.04).
  
  
  CONCLUSIONS
  The superior dosimetric outcome observed with HT appeared to translate into moderately improved clinical outcomes with respect to salivary sparing. Prospective trials are needed to validate this gain in the therapeutic ratio.
authors.affiliation: Department of Radiation Oncology, University of California Davis Cancer Center, Sacramento, CA 95817, USA. allen.chen@ucdmc.ucdavis.edu
authors.forename: A M
authors.initials: AM
authors.lastname: Chen
authors.forename: C C
authors.initials: CC
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Marsano
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.forename: J A
authors.initials: JA
authors.lastname: Purdy
mesh_terms: D000328:Adult; D000368:Aged; D001933:Brain Stem / Q000033:anatomy & histology / Q000528:radiation effects; D002277:Carcinoma; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009364:Neoplasm Recurrence, Local / Q000209:etiology; D009929:Organ Size; D059351:Organ Sparing Treatments; D058958:Organs at Risk / Q000033:anatomy & histology / Q000528:radiation effects; D010306:Parotid Gland / Q000033:anatomy & histology / Q000528:radiation effects; D011788:Quality of Life; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D013116:Spinal Cord / Q000033:anatomy & histology / Q000528:radiation effects; D016019:Survival Analysis; D013702:Temporal Lobe / Q000033:anatomy & histology / Q000528:radiation effects; D016896:Treatment Outcome; D055815:Young Adult