title: Critical analysis of locoregional failures following intensity-modulated radiotherapy for nasopharyngeal carcinoma.
abstract: OBJECTIVE
  To analyze the patterns of locoregional failure following intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) at our institution, as part of an internal quality assurance program. We aimed to investigate the potential existence of a correlation between any part of the IMRT process and clinical outcome.
  
  
  METHODS
  A total of 106 non-metastatic NPC patients consecutively treated with IMRT (with or without chemotherapy) were analyzed. Radiotherapy was administered using a sequential or simultaneous integrated boost approach at the total prescribed dose of 66-70 Gy (2.00-2.12 Gy per fraction). MRI studies of recurrences were recorded with the planning computed tomography studies to identify volume of failure. Recurrence-related characteristics were analyzed with respect to the original treatment. Failures were classified as 'in-field', 'marginal' or 'out-field' if at least 95, 20-95 or less than 20% of the volume of failure, respectively, was within 95% of the total prescription dose.
  
  
  RESULTS
  With a median follow-up of 43.4 months, 5-years local control, regional control, locoregional control and overall survival rates were 87.7, 88.0, 83.5 and 81.3% respectively. A total of 21 failures were registered in 15 patients. In particular, ten failures (47.6%) were classified as 'in-field' (seven local failures and three regional failures [RFs]), nine failures (42.9%) as 'marginal' (five local failures and four RFs) and only two failures (9.5%) as 'out-field' (both RFs). The most relevant causes of failures were suboptimal target definition and target coverage as well as a longer than planned overall treatment time.
  
  
  CONCLUSIONS
  IMRT determines excellent outcome in NPC patients. However, great attention in all IMRT steps is necessary to reduce potential causes of failure.
authors.affiliation: Radiotherapy 2, Fondazione IRCCS Istituto Nazionale dei Tumori, Via Venezian 1, 20133 Milan, Italy. ester.orlandi@istitutotumori.mi.it
authors.forename: Ester
authors.initials: E
authors.lastname: Orlandi
authors.forename: Stefano
authors.initials: S
authors.lastname: Tomatis
authors.forename: Paolo
authors.initials: P
authors.lastname: Potepan
authors.forename: Paolo
authors.initials: P
authors.lastname: Bossi
authors.forename: Valeria
authors.initials: V
authors.lastname: Mongioj
authors.forename: Mauro
authors.initials: M
authors.lastname: Carrara
authors.forename: Mauro
authors.initials: M
authors.lastname: Palazzi
authors.forename: Marzia
authors.initials: M
authors.lastname: Franceschini
authors.forename: Cristiana
authors.initials: C
authors.lastname: Bergamini
authors.forename: Laura
authors.initials: L
authors.lastname: Locati
authors.forename: Eva
authors.initials: E
authors.lastname: Iannacone
authors.forename: Marco
authors.initials: M
authors.lastname: Guzzo
authors.forename: Tullio
authors.initials: T
authors.lastname: Ibba
authors.forename: Flavio
authors.initials: F
authors.lastname: Crippa
authors.forename: Lisa
authors.initials: L
authors.lastname: Licitra
authors.forename: Emanuele
authors.initials: E
authors.lastname: Pignoli
authors.forename: Carlo
authors.initials: C
authors.lastname: Fallai
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000175:diagnosis / Q000401:mortality / Q000532:radiotherapy*; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012008:Recurrence; D017211:Treatment Failure; D055815:Young Adult