Parotid area lymph node metastases from preliminarily diagnosed patients with nasopharyngeal carcinoma: report on tumor characteristics and oncologic outcomes

The parotid area lymph node (PLN) is an uncommon site of metastasis originating from nasopharyngeal carcinoma (NPC). The study aimed to investigate clinical characteristics and outcomes of patients with preliminarily diagnosed NPC with PLN metastases. Here we retrospectively reviewed Magnetic resonance imaging (MRI) scans of 2221 patients with untreated nonmetastatic NPC who received intensity-modulated radiation therapy (IMRT). Finally, 64 (2.9%) patients were identified with PLN metastases, of which, 34 received PLN-sparing IMRT and 30 received PLN-radical IMRT. We also found that 42.2% had N3 disease and 95.3% had stages III-IVb. PLN metastases on MRI were characterized by ipsilateral retropharyngeal lymph node (RLN) or level II nodal extracapsular spread (ECS), ipsilateral giant cervical nodes, ipsilateral parapharyngeal extension, or solitary parotid metastasis. The 5-year overall survival, distant metastasis-free survival, regional relapse-free survival, and parotid relapse-free survival rates were 70.4%, 64.3%, 76.7%, and 87.9%, respectively. Distant metastases were the main cause of treatment failure and death. Using PLN-sparing IMRT, sparing PLN with minimal axial diameter of <10 mm, could increase the risk of parotid recurrence. However, it was not an independent prognostic factor. N classification and concurrent-based chemotherapy were almost statistically significant for distant failure and death. Overall, we demonstrated that the PLN metastases might be derived from RLN or level II nodal ECS, giant cervical nodes in a retrograde fashion, or parapharyngeal extension. Sparing PLN of <10 mm by IMRT should consider the risk of parotid recurrence. Distant metastases remained the dominant treatment failure. Further effective systemic chemotherapy should be explored.