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Is There a Role of Adjuvant Therapy for the Treatment of Salivary Duct Carcinoma?

Objectives: Salivary duct carcinoma (SDC) is a highly malignant tumor arising from the ductal epithelium of the salivary gland. The treatment of SDC is surgical excision along with lymph node dissection, followed by post-operative radiation and/or systemic chemotherapy. Despite the multidisciplinary approach, prognosis is poor and the role of adjuvant therapy is controversial. The objective of this study was to retrospectively analyze the role of postoperative radiotherapy/chemotherapy for the treatment of SDC. Methods: 26 patients (16 parotid gland, 8 submandibular gland, 2 minor salivary gland) with SDC were treated. The clinical stage was stage I:1 case, stage II:2cases, stage III:7 cases, stage IV:16 cases. All patients underwent surgery with neck dissection. 19 patients received post-operative radiotherapy and 13 patients received post-operative chemotherapy (CDDP/DOC: 3 cases, CDDP/ADM/CPA: 8 cases, S-1:1 case). Results: The overall 3-year and 5-year survival rate was 54% and 48.1% respectively. Among the 14 fatal cases, there were 5 cases with local recurrence and 9 cases with distant metastasis. The overall 3-year survival of the patients with or without post-operative radiotherapy was 64% and 33% respectively (P = 0.29). The overall 3-year survival of the patients with or without post-operative chemotherapy was 53% and 56% respectively (P = 0.78). Conclusions: In our retrospective analysis, there was no benefit of post-operative adjuvant therapy for SDC patients. Despite of the multidisciplinary approach, most patients recur locally or with distant metastasis. Developing novel treatment modalities (including molecular targeting) is necessary to improve the prognosis of this disease and will be discussed.