Adjuvant Radiation Therapy for High-Grade and/or Locally Advanced Major Salivary Gland Tumors

Objective: To examine the effect of adjuvant radiation therapy (RT) on survival of high-grade and/or locally advanced malignant major salivary gland tumors (MMSGT). Patients: The study population comprised 2170 patients with high-grade (poorly differentiated or undifferentiated) and/or locally advanced MMSGT (T3/4 or N+). Main Outcome Measures: The Surveillance, Epidemiology, and End Results registry was used to obtained data for all patients 20 years or older who underwent surgery for high-grade and/or locally advanced nonmetastatic MMSGT between 1988 and 2005. Univariate and multivariable regression analyses were performed to identify factors associated with improved survival. Results: Seventy-two percent of patients received adjuvant RT, while 28% underwent surgery alone. Patients receiving adjuvant RT were younger and had higher T and N categories and grade. Multivariable analysis revealed significantly improved survival with adjuvant RT (HR for mortality, 0.76; 95% CI, 0.65-0.89; P < .001). Other factors associated with improved survival included younger age at diagnosis, less than radical surgery, certain histologic subtypes, lower grade, and lower T and N categories. Subset analyses found significantly improved survival with adjuvant RT among patients with both high-grade and locally advanced disease ( P < .001), involvement of the parotid gland (P=.002), or squamous cell carcinoma (P=.004), with a survival benefit seen among patients with adenocarcinoma that did not reach significance (P=.06). Conclusions: Adjuvant RT is associated with improved survival for high-grade and/or locally advanced MMSGT based on analysis of this large, population-based database. Further prospective studies are warranted to examine the role of RT in the management of this disease.