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PURPOSE The purpose of this study was to analyze the effectiveness and safety of the combination of surgery plus postoperative iodine-125 interstitial brachytherapy for treatment of adenoid cystic carcinoma (ACC) of the parotid. METHODS AND MATERIALS This study included a retrospective analysis of the data of patients who underwent postoperative iodine-125 interstitial brachytherapy for histology-confirmed ACC of the parotid between January 2002 and November 2018 in Peking University Hospital of Stomatology. Acute and long-term radiation-related toxicities were assessed by the criteria of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer. Multivariate analysis was used to identify the factors affecting overall survival, disease-free survival (DFS), and distant metastasis-free survival (DMFS). RESULTS A total of 86 patients (53 women; median age 50 years, SD = 13.1) were included. Median followup was for 45.5 months. About half the patients (44/86, 51.3%) had clinical stage IV disease. Local recurrence occurred in 11 of 86 (12.8%) patients. No patient had nodal metastases in the followup period. The five- and 10-year DFS rates were 74.8% and 66.6%, respectively. The mean DMFS was 60.6 months. On multivariate analysis, preoperative facial palsy, type of surgery, perineural spread (PNS), and distant metastases were independent prognostic factors for DFS; preoperative facial palsy, nodal metastases, and PNS were independent prognostic factors for overall survival; and preoperative facial palsy, type of surgery, PNS, and pathological type were independent prognostic factor for DMFS. CONCLUSIONS The combination of surgery and iodine-125 interstitial brachytherapy appears to be an effective and safe treatment for primary ACC of the parotid.