Distributions of Cervical Lymph Node Metastases in Oropharyngeal Carcinoma: Therapeutic Implications for the N0 Neck

Abstract

OBJECTIVES: This study sought to investigate the patterns and distributions of lymph node metastases in oropharyngeal squamous cell carcinoma (SCC) and improve the rationale for elective treatment of N0 neck. MATERIALS AND METHODS: One hundred four patients with oropharyngeal SCC who underwent neck dissection between 1992 and 2003 were analyzed retrospectively. All patients had curative surgery as their initial treatment for the primary tumor and neck. A total of 161 neck dissections on both sides of the neck were performed. Therapeutic dissections were done in 71 and 5 necks and elective neck dissection was done on 33 and 52 necks on the ipsilateral and contralateral sides, respectively. Surgical treatment was followed by postoperative radiotherapy for 78 patients. The follow-up period ranged from 1 to 96 months (mean, 30 months). RESULTS: Of the 161 neck dissection specimens evaluated, 90 (56%) necks were found to have lymph node metastases found by pathologic examination. These consisted of 76 (73% of 104 necks) of the ipsilateral side and 14 (25% of 57 necks) of the contralateral side dissections. The occult metastatic rate was 24% (8 of 33) of ipsilateral neck samples and 21% (11 of 52) of contralateral neck samples. Of the 68 patients who had a therapeutic dissection on the ipsilateral side and had lymphatic metastasis, the incidence rate of level IV and level I metastasis was 37% (25 of 68) and 10% (7 of 68), respectively. Isolated metastasis to level IV occurred on the ipsilateral side in three patients. There were no cases of isolated ipsilateral level I pathologic involvement in an N-positive neck or occult metastasis to this group. The incidence rate of level IV metastasis in patients with ipsilateral nodal metastasis was significantly higher in base of tongue cancer (86% [6 of 7]) compared with tonsillar cancer (34% [20 of 59]) (P=.013). Patients with level IV metastasis had significantly worse 5-year disease-free survival rates than patients with metastasis to other neck levels (54% versus 71%; P=.04). CONCLUSION: These results suggest that elective N0 neck treatment in patients with oropharyngeal SCC, especially base of tongue cancer, should include neck levels II, III, and IV instead of levels I, II, and III.