Prediction of Occult Contralateral Nodal Metastasis in Surgical Treated p16 Negative Oropharyngeal Squamous Cell Carcinoma

BACKGROUND: It is well known that p16 negative oropharyngeal squamous cell carcinoma (OPSCC) has a high probability of spreading to the ipsilateral neck. However, no consensus exists as to whether to perform elective treatment for clinical nodal negative in contralateral neck. METHODS: A total of 85 patients with p16 negative OPSCC who underwent primary tumor excision and bilateral neck dissections between 2005 and 2018 were analyzed retrospectively. Clinicopathologic variables were used to identify factors predicting occult contralateral nodal metastasis (OCNM). A nomogram was developed to assess the risk of OCNM and the model was validated internally by using bootstrap resampling. RESULTS: The overall prevalence of pathologically positive contralateral nodes was 30.6% (26/85) in our cohort, and the rate of OCNM was 18.3% (11/60). The presence of ipsilateral clinical extranodal extension (cENE) was significantly associated with contralateral neck metastasis (odds ratio, 5.662; 95% CI, 2.079–15.415) with increased risk of OCNM (odds ratio, 4.271; 95% CI, 1.045–17.458). Moreover, the concordance index of the proposed nomogram model without ipsilateral cENE was 0.623 and could increase to 0.717 with the inclusion of ipsilateral cENE in the calculation. CONCLUSION: The risk of OCNM in p16 negative OPSCC with ipsilateral cENE is notable. Ipsilateral cENE-based nomogram might assist in individual decision-making regarding contralateral nodal negative neck management and help avoid the over- and under-treatment of p16 negative OPSCC.