Radiotherapy for nonadenoid cystic carcinomas of major salivary glands.

PURPOSE: To report outcomes in patients treated with postoperative radiotherapy for nonadenoid cystic carcinomas of the major salivary glands. MATERIALS AND METHODS: From 1998-2011, 37 patients with nonadenoid cystic carcinomas of the major salivary gland underwent postoperative radiotherapy. The median radiation dose was 60 Gy (range, 45-70 Gy). TNM distribution included T1-2 (n=16, 44%), T3-T4 (n=21, 56%), N0 (n=19, 51%), and N+ (n=18, 49%). Histologies included adenocarcinoma (n=13, 35%), squamous cell carcinoma (n=8, 22%), mucoepidermoid carcinoma (n=8, 22%), and other (n=8, 21%). Median follow-up was 4.7 years for all patients (range, 0.3-14.1 years) and 5.0 years for living patients (range, 1.2-12.2 years). RESULTS: Five-year local-regional control, overall survival (OS), and cancer-specific survival (CSS) were 97%, 76%, and 84%. On univariate analysis, OS was significantly worse for patients >/=65 years old (p=0.04). CSS was significantly worse for positive perineural invasion (p=0.02), extraparenchymal extension (p=0.04), and in patients who received no chemotherapy (p=0.02). Doses >60 Gy was significantly worse for OS (p=0.003) and CSS (p=0.003), although these patients had higher TNM (>T2, p=0.01) and trended towards a higher rate of extraparenchymal extension (p=0.08). Four patients (11%) developed >/=grade 2 toxicities; 3 patients developed early toxicities and one patient developed late toxicities. CONCLUSIONS: Radiotherapy for salivary gland tumors provides excellent local-regional control when combined with surgery. Distant metastasis is the predominant pattern of failure, although chemotherapy seemed to improve cancer-specific survival.