Prognosis and staging of parotid lymph node metastasis in nasopharyngeal carcinoma: An analysis in 10,126 patients

Objective: In nasopharyngeal carcinoma (NPC), the staging category of parotid lymph node (PLN) metastasis is not explicitly defined, resulting in varied classifications and treatment strategies in clinical practice. This study aimed to determine the prognostic value and optimal staging category of PLN metastasis in NPC. Materials and methods: With the NPC database from a big-data platform, 10,126 patients with primarily diagnosed, non-metastatic NPC and treated with intensity modulated radiotherapy at our center from 2009 to 2015 were analyzed in this study. Results: In total, 43/10126 patients (0.4%) were diagnosed with histologically verified PLN metastasis at initial diagnosis. Of these, 88.4% (38/43) had enlarged lymph nodes in level II and 34.9% (15/43) in level Ib. Compared with patients without PLN metastasis, those with PLN metastasis had higher risk of disease failure (adjusted hazard ratio [HR], 1.770), distant metastasis (HR, 1.907), and regional recurrence (HR, 3.649), with similar 3-year disease-free survival (70.0% vs. 71.1%) and distant metastasis-free survival (74.8% vs. 77.4%) with patients with N3 disease. Of note, 10/43 patients had regional recurrence: six had recurrent lymph nodes in level Ib; and four of these six patients had no identifiable level Ib lymph nodes on pretreatment imaging. Conclusion: PLN metastasis was associated with high risk of distant metastasis and regional recurrence, and patients with PLN metastasis had similar outcome compared with patients with N3 disease. Regional recurrences in rare levels, such as level Ib, were common in patients with PLN metastasis at initial diagnosis.