[Impact of neck dissection in N2-3 oropharyngeal squamous cell carcinomas treated with definitive chemoradiotherapy: An observational real-life study].

PURPOSE: The purpose of this study was to assess the efficacy in terms of neck failure of an initial neck dissection before definitive chemoradiotherapy in N2-3 oropharyngeal squamous cell carcinomas, as well as the dosimetric impact and the acute and delayed morbidity of this approach.

MATERIALS AND

METHODS

All patients consecutively treated between 2009 and 2018 with definitive chemoradiotherapy using intensity-modulated conformal radiotherapy (IMRT) for a histologically proven N2-3 oropharyngeal squamous cell carcinomas were retrospectively included. The therapeutic approach consisted of induction chemotherapy, followed by cisplatine-based chemoradiotherapy preceded or not by neck dissection. Neck dissection was discussed on a case-by-case basis in a dedicated multidisciplinary tumour board for patients with a dissociated response to induction chemotherapy, defined as a better response on the primary than on the node. Chemoradiotherapy without neck dissection was systematically performed in case of a major lymph node response to induction chemotherapy (decrease in size of 90% or more). Intensity-modulated radiotherapy using a simultaneous-integrated boost delivered 70Gy in 35 fractions on macroscopic tumour volumes, 63Gy on intermediate-risk levels or extra-nodal extension and 54Gy on prophylactic lymph node areas.

RESULTS

Two groups were constituted: 47 patients without an initial neck dissection (62.7%), and 28 patients with a neck dissection prior to definitive chemoradiotherapy (37.3%). Initial patient characteristics were not statistically different between the two groups. The median follow-up was 60.1months (range: 3.2-119months). Incidence of neck failure was higher in patients without neck dissection (P=0.015). The neck failure rate at 5years was 19.8% (95% confidence interval: 7.4-30.6%; P=0.015) without neck dissection versus 0% following neck dissection. All lymph node failures occurred in the planned target volume at 70Gy. Upfront neck dissection suggested a decrease in the mean dose received by the homolateral parotid gland (P=0.01), mandible (P=0.02), and thyroid gland (P=0.02). Acute toxicity of chemoradiotherapy after neck dissection suggested a reduction in grade≥3 adverse events (P=0.04), early discontinuation of concomitant chemotherapy (P=0.009) and feeding tube-dependence (P=0.008) in univariate analysis. During follow-up, there was no difference between the two groups in terms of xerostomia, dysgeusia, dysphagia or gastrostomy dependence in univariate analysis.

CONCLUSION

Neck dissection prior to definitive chemoradiotherapy in N2-3 oropharyngeal squamous cell carcinoma was associated with high neck control without additional mid and long-term morbidity.