Low-Grade Salivary Gland Cancers: Treatment Outcomes, Extent of Surgery and Indications for Postoperative Adjuvant Radiation Therapy

Background Histologic grade of tumor is one of the major prognostic predictors for patients with salivary gland cancer. Because of disease rarity, little is known about the optimal treatment modalities and outcomes in low-grade salivary gland cancers (LGSGC). We tried to identify prognostic factors, and the adequate treatment modalities and outcomes in pathologically confirmed LGSGC patients. Methods We retrospectively extracted the clinical and pathology data from 179 LGSGC cases from 1995 to 2013. Pathological features, such as extraparenchymal extension, perineural/nerve invasion, lymphovascular invasion/tumor emboli, and resection margin status were redefined for each case. Risk factors for recurrence, extent of surgery, and the role of postoperative radiation therapy were analyzed. Results Recurrence-free survival and overall survival were 89.6 and 96.6 % at 10 years, respectively. The presence of regional nodal metastasis and positive cancer cells at resection margin were significant unfavorable prognostic factors. Postoperative adjuvant radiation treatment significantly reduced recurrences, particularly in cases with pathology risk factors (perineural invasion, lymphovascular invasion, extraparenchymal extension, or cancer cells at the resection margin), node metastasis, and advanced T-stage tumors. Close surgical margin