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

Authors


  • 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.

Correspondence

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

Email: daisy.mak@petermac.org

Abstract

Introduction

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%.

Conclusion

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.

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