title: Treatment response in the neck: p16+ versus p16- oropharyngeal cancer.
abstract: BACKGROUND
  To compare nodal response rates following chemoradiotherapy in patients with p16+ and p16- oropharyngeal squamous cell carcinoma (OPSCC).
  
  
  METHODS
  Patients with node-positive OPSCC treated at Peter MacCallum Cancer Centre on the published phase I-III tirapazamine trials were identified. All patients had conventional assessment (clinical examination (CA), CT and/or MRI) and positron emission tomography (PET) at both baseline and 2-4 months post-treatment.
  
  
  RESULTS
  There were 30 p16+ and 18 p16- patients, the former group having significantly higher stage nodal disease (P = 0.016). The mean overall reduction in nodal size at post-treatment assessment was similar in p16+ and p16- patients (78% vs. 75%), and no statistically significant difference in nodal complete response (CR) rates was detected by either CA (50% vs. 39%, P = 0.35) or PET/PET-CT (93% vs. 83%, P = 0.19). PET was significantly more accurate in determining the true nodal CR rate in both groups, with a negative predictive value of 96%.
  
  
  CONCLUSIONS
  Nodal response rates following chemoradiotherapy appear to be similar in p16+ and p16- patients when assessed by either CA or PET/PET-CT. However, higher nodal CR was seen in PET/PET-CT compared with CA in both groups. Metabolic imaging is more accurate than CA in assessing nodal response post-treatment.
authors.affiliation: Department of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia. daisy.mak@petermac.org
authors.forename: Daisy
authors.initials: D
authors.lastname: Mak
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Hicks
authors.forename: Danny
authors.initials: D
authors.lastname: Rischin
authors.forename: Ben
authors.initials: B
authors.lastname: Solomon
authors.forename: Lester
authors.initials: L
authors.lastname: Peters
authors.forename: Mathias
authors.initials: M
authors.lastname: Bressel
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Young
authors.forename: June
authors.initials: J
authors.lastname: Corry
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000032:analysis*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy*; D059248:Chemoradiotherapy / Q000379:methods; D019941:Cyclin-Dependent Kinase Inhibitor p16; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000032:analysis*; D009959:Oropharyngeal Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000628:therapy*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use; D000077704:Tirapazamine; D016896:Treatment Outcome; D014227:Triazines / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C000614131:CDKN2A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009363:Neoplasm Proteins; D011838:Radiation-Sensitizing Agents; D014227:Triazines; D000077704:Tirapazamine