The influence of HPV-associated p16-expression on accelerated fractionated radiotherapy in head and neck cancer: evaluation of the randomised DAHANCA 6&7 trial

Abstract

Background and purpose: Tumour HPV-positivity is a favourable prognostic factor in the radiotherapy of HNSCC, but the optimal radiotherapy regimen for HPV-positive HNSCC is not yet defined. Reducing overall treatment time is known to improve outcome in the radiotherapy of HNSCC as was also demonstrated in the randomised DAHANCA 6&7 trial. We aimed to assess the influence of tumour HPV-status, expressed by p16, on the response to accelerated fractionated radiotherapy in HNSCC through evaluation of the DAHANCA 6&7 trial.

Materials and methods: Immunohistochemical detection of HPV-associated p16-expression was performed on FFPE-pre-treatment tumour-tissues from 794 patients enrolled in the DAHANCA 6&7 trial. The influence of tumour p16-status on loco-regional tumour control and survival as a function of fractionation schedule (5Fx/week vs 6Fx/week) was evaluated 5years after the completion of radiotherapy.

Results: The significant and independent prognostic value of tumour p16-positivity in HNSCC radiotherapy was confirmed, with adjusted hazard ratios (HR) of 0.58 [0.43-0.78], 0.47 [0.33-0.67] and 0.54 [0.42-0.68] for loco-regional control, disease-specific and overall survival, respectively. Accelerated radiotherapy significantly improved loco-regional tumour control compared to conventional radiotherapy, adjusted HR: 0.73 [0.59-0.92] and the benefit of the 6Fx/week regimen was observed both in p16-positive (HR: 0.56 [0.33-0.96]) as well as in p16-negative tumours (HR: 0.77 [0.60-0.99]). Disease-specific survival was also significantly improved with accelerated radiotherapy in the group of p16-positive tumours (adjusted HR: 0.43 [0.22-0.82]).

Conclusion: Accelerated radiotherapy significantly improves outcome in HNSCC compared to conventional fractionation. The observed benefit is independent of tumour p16-status and the use of a moderately accelerated radiotherapy regimen seems advantageous also for HPV/p16-positive HNSCC.