Supplementary Material for: Survival Outcome of Intermediate-Grade Salivary Gland Carcinoma

Objective: Histological grade is the most important factor for defining treatment strategies and predicting prognosis for salivary gland carcinoma (SGC). We examined factors affecting long-term recurrence and survival among intermediate-grade SGC (IGSGC) patients to define optimal treatment modalities and outcomes. Methods: We reviewed the clinical and pathological data on 108 IGSGC patients who underwent definitive surgery with or without postoperative radiotherapy. We compared treatment outcomes by treatment strategies such as surgical extent for the primary tumor, neck dissection, or postoperative radiotherapy. Results: During a 103-month median follow-up, local, regional, and distant recurrences were detected in 14 (13.0%), 3 (2.8%), and 21 (19.4%) patients, respectively. The 10-year locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS) rates were 83.1, 76.0, and 80.1%, respectively. Multivariate analyses identified a nonparotid primary site as an independent prognostic factor for LRC (p = 0.018). Adenoid cystic carcinoma and a positive pN classification were significantly unfavorable prognostic factors for DMFS (p = 0.025 and p = 0.030, respectively); overall advanced stage was an independent prognostic factor for OS (p = 0.020). Surgical extent, elective neck dissection, and postoperative adjuvant radiotherapy did not significantly affect treatment outcomes. Conclusion: Patients with early-stage IGSGC of parotid origin can achieve favorable treatment outcomes with conservative surgery alone.