Prevalence and distribution of cervical lymph node metastases in HPV-positive and HPV-negative oropharyngeal squamous cell carcinoma.

OBJECTIVE: In oropharyngeal squamous cell carcinoma (OP-SCC), the prevalence and distribution of clinical and pathological lymph node metastasis in the neck have been extensively reported. It served as the basis for consensus recommendations on the selection of the lymph node levels in the neck requiring a treatment. The objective of the study is to compare the prevalence and distribution of neck node metastases in HPV+ and HPV- OP-SCC from a large series of patients with OP-SCC who underwent a cervical lymph-node dissection (LND) as part of their treatment.

METHODS: The study concentrated on OP-SCC patients treated by various neck node dissection (LND) procedures from January 2014 to December 2018 in 3 French institutions. Patients with prior head and neck cancer, prior neck surgery, the use of induction chemotherapy, or patients with carcinoma of unknown primary were excluded. HPV-status was assessed by p16 immunohistochemistry. For each patient, the clinical and the pathological nodal status, as well as the distribution of the positive nodes in each neck level (from Ia to V) were reported.

RESULTS: Two-hundred and sixty-three patients were included (126 p16-negative (p16-), and 137 p16-positive (p16+). The rate of clinical positive node (cN+) reached 54% and 88.3% in the p16- and p16+ groups, respectively (p < 0.001); the corresponding rate of pathological positive node (pN+) reached 61.9% and 91.2%, respectively (p < 0.001). Regarding the clinical lymph node distribution, in p16+ patients, more positive nodes were observed in the ipsilateral level IV (p = 0.003), and less positive nodes were observed in the contralateral levels III and IV (p = 0.003 and p = 0.045, respectively). Regarding the pathologic lymph node distribution in the ipsilateral neck, in the cN0 patients, no significant difference was observed between p16- and p16+ patients (p = 0.33 to 1); in the cN+ patients, the nodes were distributed in levels Ib, II, III, IV and V without differences between the p16- and the p16+ patients. In the contralateral neck of p16- patients, nodes metastases were mainly observed in levels II, III and IV, whereas for the p16+ patients, positive nodes were only observed in level II (p = 0.03).

CONCLUSION: This study demonstrated the higher prevalence of cN+ and pN+ in p16+ OP-SCC patients, but without meaningful difference in the distribution of the lymph node drainage between p16- and p16+ OP-SCC. It indicates that no difference should be made between p16- and p16+ patients regarding the extend of neck treatment.