Treatment response in the neck: p16+ versus p16− oropharyngeal cancer


  • D Mak MBBS, FRANZCR; RJ Hicks MBBS, MD, FRACP; D Rischin MBBS, MD, FRACP; B Solomon MBBS, PhD; L Peters MD, FRANZCR; M Bressel MSc; RJ Young BSc (Hons); J Corry FRANZCR, MD.
  • Conflict of interest: No conflict of interest.


Dr Daisy Mak, Department of Radiation Oncology, Peter MacCallum Cancer Centre, Locked Bag 1, A'Beckett Street, East Melbourne, Vic. 8006, Australia.




To compare nodal response rates following chemoradiotherapy in patients with p16+ and p16− oropharyngeal squamous cell carcinoma (OPSCC).


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.


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%.


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.