Impact of contralateral occult neck metastasis in HPV-associated tonsil cancer: Is elective contralateral neck dissection required?

Background: Contralateral elective neck dissection in human papillomavirus (HPV)- associated tonsil cancer is a matter of debate. Objectives: The aim of this study was to analyze rates of contralateral lymph node (LN) metastasis and their prognostic effects on HPV-associated tonsil cancer. We also assessed the necessity of elective contralateral neck dissection. Methods: To investigate the pathologic incidence of and risk factors for contralateral nodal disease in HPV-associated tonsil cancer treated with upfront primary surgery and bilateral neck dissection, the records of 68 patients were reviewed. Results: Six (8.8%) patients displayed pathologic contralateral nodal disease; four of the patients had LN metastasis confirmed in contralateral level II, one patient had LN metastasis in level III, and one patient had multi-level metastasis in contralateral levels II and III. Contralateral LN metastasis showed a significant association with greater depth of invasion (DOI) in primary tumor (p = 0.032), count of positive LN (p = 0.008), and positive LN ratio of the ipsilateral neck (p = 0.01). Patients with contralateral LN metastasis showed a significantly worse five-year overall survival but no significant difference in disease-free survival. Conclusion: HPV-associated tonsil cancer has exceedingly low rates of occult contralateral LN metastasis. However, in cases of ipsilateral multiple node metastases and higher DOI, it may be worth considering elective contralateral neck dissection based on the risk of occult metastasis.