Objectives: Excellent local-regional control can be achieved for major salivary gland tumors treated with surgery and post-operative radiotherapy. We evaluated the cumulative incidence and predictors of distant metastasis in high-risk major salivary gland tumors.
Methods: Between 1990 and 2011, 200 patients with major salivary gland tumors received post-operative radiotherapy at our center. The patients' median age was 60 years. Patients had primary tumors of the parotid gland (84%), submandibular (16%), and one sublingual gland. Among the patients, 34% had T3-T4 tumors, 32% had nodal involvement. Other high-risk features included close/positive margins and high grade tumors. The median RT dose was 63 Gy.
Results: With a median follow-up of 50 months, the 5-year local control and regional control were 88% and 94%, respectively. The 5-year freedom from distant metastasis was 73%. The median overall survival was 14.6 years corresponding to a 5 and 10-year overall survival of 77% and 59%, respectively. T category and nodal involvement were independent predictors of distant metastasis. Nodal involvement was also an independent predictor of overall survival.
Conclusions: Distant relapse was the predominant mode of failure despite excellent local-regional control in high-risk major salivary gland tumors. Both advanced T category and nodal involvement were independent predictors of distant metastasis. More effective systemic therapy is needed to combat distant relapse.
Keywords: distant metastasis; major salivary gland tumors; parotid gland; radiation therapy; systemic therapy.