Determinants and Patterns of Survival in Adenoid Cystic Carcinoma of the Head and Neck, Including an Analysis of Adjuvant Radiation Therapy

Objectives: The effect of adjuvant radiation therapy (RT) on survival in patients with adenoid cystic carcinoma (ACC) is much debated. Studies with large numbers of patients and long follow-up are lacking in the literature. Methods: We identified 2286 single-primary ACCs of the head and neck treated with surgery in the National Cancer Institute's surveillance, epidemiology, and end results database. The determinants of survival, including the effect of adjuvant RT, were analyzed with a Cox Proportional Hazards Model. Results: The overall 5-, 10-, 15-, 20-, and 25-year survival rates for patients receiving surgical resection were 77.3%, 59.6%, 44.9%, 35.0%, 25.5%, respectively. In the interval between 10 and 30 years after diagnosis, 111 patients died of ACC, and 137 died of all competing causes combined. Increasing stage caused a decrease in survival that was proportional over time. On multivariable analysis, distant metastasis, lymph node involvement, higher T classification, increasing age, and submandibular gland, or sinus/nasal cavity subsites were each independently associated with decreased overall and cause-specific survival. Adjuvant RT failed to improve overall or cause-specific survival. Conclusions: Cause-specific survival continues to decline up to 30 years after diagnosis in ACC of the head and neck. In the interval between 10 and 30 years after diagnosis, patients are nearly as likely to die of ACC as from all competing causes combined. Certain clinicopathological factors are associated with decreased survival. There is no evidence of increased survival in patients receiving adjuvant RT.