Cervical Lymph Node Metastatic Status and Adjuvant Therapy Predict the Prognosis of Salivary Duct Carcinoma

Purpose: Salivary duct carcinoma (SDC) is an aggressive malignancy that is not yet fully understood. We designed the present retrospective study to investigate the factors affecting the prognosis of SDC and the effects of adjuvant therapies on the clinical outcomes of patients. Materials and Methods: Patients with SDC treated surgically from 2006 to 2016 were enrolled in the present retrospective cohort study. The demographic data, clinical pathologic characteristics, and followup results were recorded. The prognostic indicators of overall survival (OS), locoregional failure-free survival (LRFFS), and distant metastasis-free survival (DMFS) were analyzed using the Kaplan-Meier method and the Cox proportional hazard model. Results: The study sample included 66 patients, most of whom were male (81.8%). The 5-year OS, LRFFS, and DMFS for all patients was 52.5%, 63.9%, and 51.3%, respectively. Univariate analysis showed that stage N2-N3, lymph node involvement of levels IV and V, 8 or more positive lymph nodes, and extra-nodal extension were all negative prognostic indicators for OS. The only significant indicator on multivariate analysis was the number of positive lymph nodes. Multivariate analysis revealed that extracapsular invasion and no adjuvant radiotherapy were risk factors for LRFFS. In contrast, lesions involving both glands and 8 or more positive lymph nodes were prognostic factors for DMFS. Further subgroup analysis showed that radiotherapy was only useful for patients with locally advanced lesions for local control. Conclusions: Cervical lymph node metastatic status is an important factor in predicting the prognosis of SDC patients. Adjuvant radiotherapy is useful for local control, especially for patients with stage T4 disease but does not benefit OS and DMFS. (C) 2018 American Association of Oral and Maxillofacial Surgeons