The role of postoperative radiation therapy in carcinoma ex pleomorphic adenoma of the parotid gland.

Abstract

To evaluate the impact of postoperative radiation therapy on the clinical course of patients with carcinoma ex pleomorphic adenoma of the parotid gland. Between 1960 and 2004, 63 patients were treated with definitive surgery for carcinoma ex pleomorphic adenoma of the parotid gland. Forty patients (63%) received postoperative radiation therapy to a median dose of 60 Gy (range, 45-71 Gy). Adenocarcinoma (29 patients), salivary duct carcinoma (16 patients), and adenoid cystic carcinoma (9 patients) were the most common malignant subtypes. Pathologic T -stage was: 16% T1, 33% T2, 32% T3, and 19% T4. Twenty-one patients (33%) had microscopically positive margins and 39 (62%) had perineural invasion. Median follow-up was 50 months (range, 2-96 months). The use of postoperative therapy significantly improved 5-year local control from 49% to 75% (p = 0.005) and was associated with an improvement in survival among patients without evidence of cervical lymph node metastasis (p = 0.01). A Cox proportional hazard model identified pathologic involvement of cervical lymph nodes as an independent predictor of overall survival. Overall survival was 16% for patients with pathologic N-positive disease compared with 67% for those whose lymph node status was negative or unknown (p = 0.001). Surgery followed by postoperative radiation should be considered the standard of care for patients with carcinoma ex pleomorphic adenoma.