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

Purpose: To evaluate the impact of postoperative radiation therapy on the clinical course of patients with carcinoma ex pleomorphic adenoma of the parotid gland. Methods and Materials: 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). Results: 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). Conclusion: Surgery followed by postoperative radiation should be considered the standard of care for patients with carcinoma ex pleomorphic adenoma.