title: Patterns-of-failure after helical tomotherapy-based chemoradiotherapy for head and neck cancer: implications for CTV margin, elective nodal dose and bilateral parotid sparing.
abstract: OBJECTIVE
  There is debate about the optimal clinical target volume (CTV) expansion and prophylactic nodal dose (PND) in head and neck IMRT. We evaluated our patterns-of-failure (POF) after helical tomotherapy-based concurrent chemoradiotherapy (CCRT) to assess the oncologic safety of reducing the CTV, PND, and bilateral parotid sparing (BPS).
  
  
  METHODS
  All patients with locally advanced squamous cell carcinoma of the head and neck treated with curative intent CCRT between January 2007 and April 2013 at a single institution were included in this retrospective study. Locoregional recurrences (LRR) were overlaid on the treatment plan, and POF was determined relative to planned dose.
  
  
  RESULTS
  One hundred and fourteen patients treated with CCRT were evaluated, 74% of whom underwent BPS. The median follow-up for surviving patients was 29.3 months. The 3-year cumulative incidence of locoregional failure, distant metastasis, progression-free and overall survival were 20%, 20%, 56% and 73% respectively. The local failures (n = 12) were either entirely contained within or centered on the original gross tumor volume (GTV), and all but 2 regional recurrences were in GTV. There were no nodal failures in the low-dose or peri-parotid neck (including ipsilateral neck).
  
  
  CONCLUSIONS
  Nearly all LRR were located within the GTV suggesting that minimal-to-zero margin is required for CTV 70. The nodal recurrence pattern suggests the safety of routine bilateral parotid sparing and relatively low biologically equivalent dose (54 Gy in 33fx) to the low-risk neck.
authors.affiliation: Rush University Medical Center, Department of Radiation Oncology, Chicago, IL, United States. Electronic address: virag_dandekar@rush.edu.
authors.forename: Virag
authors.initials: V
authors.lastname: Dandekar
authors.affiliation: Rush Medical College, Chicago, IL, United States.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Morgan
authors.affiliation: Rush University Medical Center, Department of Radiation Oncology, Chicago, IL, United States.
authors.forename: Julius
authors.initials: J
authors.lastname: Turian
authors.affiliation: Rush University Medical Center, Department of Medical Oncology, Chicago, IL, United States.
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Fidler
authors.affiliation: Rush University Medical Center, Department of Medical Oncology, Chicago, IL, United States.
authors.forename: John
authors.initials: J
authors.lastname: Showel
authors.affiliation: Rush University Medical Center, Department of Otolaryngology, Chicago, IL, United States.
authors.forename: Thomas
authors.initials: T
authors.lastname: Nielsen
authors.affiliation: Advocate Condell Medical Center, Libertyville, IL, United States.
authors.forename: Joy
authors.initials: J
authors.lastname: Coleman
authors.affiliation: Rush University Medical Center, Department of Radiation Oncology, Chicago, IL, United States.
authors.forename: Aidnag
authors.initials: A
authors.lastname: Diaz
authors.affiliation: Rush University Medical Center, Department of Radiation Oncology, Chicago, IL, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Sher
mesh_terms: D000368:Aged; D003131:Combined Modality Therapy; D005260:Female; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D006801:Humans; D008207:Lymphatic Metastasis / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000528:radiation effects*; D050397:Radiotherapy, Intensity-Modulated; D015996:Survival Rate
keywords: Combined modality therapy; Head and neck cancer; IMRT; Parotid sparing; Pattern-of-failure