Number of positive lymph nodes better predicts survival for oral cavity cancer.

BACKGROUND: We compared the predictive ability of our proposed N classification with that of the American Joint Committee on Cancer (AJCC) nodal (N) classification for oral cavity squamous cell carcinoma (OCC). METHODS: We assessed 345 OCC patients who underwent primary tumor extirpation and neck lymph node (LN) dissection. N classification was analyzed by recursive partitioning analysis and compared with the AJCC N classification by c-index. Cox proportional hazards regression analyses were used to determine associations between tumor or nodal factors and disease-free survival (DFS) or overall survival (OS). RESULTS: Positive LNs were found in 149 patients (43.2%). In multivariate models, the number of positive LNs and LN ratio strongly associated with DFS and OS (P < 0.001). Our new N classification was proposed with four categories of N0, N1 (1 positive LN), N2 (2-4 positive LNs or extranodal extension > 2 mm), and N3 (>/=5 positive LNs). The c-index for the proposed N classification showed improvement in survival predictions (0.735; 95% CI, 0.703-0.767) compared with the AJCC N classification (0.701; 0.667-0.735). CONCLUSIONS: The number of positive LNs and LN ratios strongly associated with posttreatment recurrence and survival for OCC. Using positive LN numbers with the N classification improves OCC survival predictions.