Association between factor of parotid lymph node and prognosis in parotid cancer.

INTRODUCTION: Survival significance of parotid lymph node (LN) factors in parotid cancer remains unclear, our goal was to assess the impact of number, size, and extranodal extension (ENE) of metastatic parotid LNs on prognosis in parotid cancer. MATERIALS AND METHODS: Patients with surgically treated parotid cancer were retrospectively enrolled. Primary outcome variable was recurrence-free survival (RFS) and overall survival (OS). The hazard ratios (HRs) of main predictive variables including the number, size, and ENE of positive parotid LNs on RFS and OS were analyzed using Cox model. The secondary outcome variable was ENE of metastatic parotid LN, its association with clinicopathologic variables were evaluated using Chi-square test. RESULTS: In total, 453 patients (186 male and 267 female) were included. The 10-year RFS and OS rates were 73% (95%CI: 69%-77%) and 61% (95%CI: 55%-67%), respectively. In Cox model, compared none parotid LN metastasis, one metastatic parotid LN did not offer additional compromise of RFS (p = 0.224) or OS (p = 0.135), but two or more positive LNs decreased the control of RFS (HR: 2.017; 95%CI: 1.378-4.632) and OS (HR: 2.173; 95%CI: 1.367-4.275). When accounting for the number of metastatic LNs, LN size or ENE was no longer related to RFS or OS. ENE of parotid LN tended to develop if there was presence of T3/4 stage, lymphovascular invasion, high histologic grade, N2/3 stage, and three or more positive parotid LNs. CONCLUSION: Quantitative parotid LN burden but not ENE or LN size is an important determinant of survival in patients with parotid cancer.