Postoperative adjuvant radiotherapy for adenoid cystic carcinoma of the head and neck: treatment results and prognostic factors.

Adenoid cystic carcinoma (ACC), which accounts for less than 1% of all head and neck malignancies and approximately 10% of all salivary neoplasms, was first described by Billroth in 1856 and was called cylindroma because of its unique histologic pattern. ACC of the head and neck shows a long natural course, high recurrence rates, late metastasis, and a tendency for perineural invasion. Although surgery is the main treatment for ACC of the head and neck, postoperative radiotherapy is often recommended because tumors without welldefined borders easily infiltrate into adjacent tissues. In this retrospective study, we reviewed treatPostoperative Adjuvant Radiotherapy for Adenoid Cystic Carcinoma of the Head and Neck: Treatment Results and Prognostic Factors