Supplementary Material for: Clinically Node-Negative Parotid Gland Cancers: Prognostic Factors of Survival and Surgical Extent

Objective: Conservative parotidectomy is known to reduce morbidity, but has been rarely examined in patients with clinically node-negative (cN0) parotid cancers. We evaluated the clinicopathological variables influencing the outcomes of these patients and the efficacy of conservative parotidectomy. Methods: We reviewed the clinical and pathological data of 256 patients with cN0 parotid carcinomas who underwent curative surgery at our institution. Of these, 110 and 146 underwent conservative and total parotidectomy, respectively, with 83 undergoing elective neck dissection and 135 receiving postoperative radiotherapy. Univariate and multivariate analyses of variables predicting recurrence-free survival (RFS) and overall survival (OS) were performed. Morbidity, survival, and recurrence rates were compared between the conservative and total parotidectomy groups. Results: The 5-year RFS and OS rates in all patients were 85.7 and 91.4%, respectively. Multivariate analysis showed that advanced T classification, positive resection margin, and high-histologic grade were independent prognostic factors for both RFS and OS. Among the 201 patients with low- or intermediate-grade parotid cancers, those who underwent total parotidectomy had a greater chance of facial nerve paralysis than those who underwent conservative parotidectomy (p < 0.001). The 5-year RFS and OS after conservative parotidectomy (93.7 and 100%, respectively) were not worse than those after total parotidectomy (85.5 and 90.9%, respectively). Conclusion: Patients with cN0 parotid cancers may be stratified by histological grade and T classification. Conservative parotidectomy may be suitable for early T1–2 low- or intermediate-grade tumors if a resection margin is secured.