Role for Postoperative Radiation Therapy in Adenoid Cystic Carcinoma of the Head and Neck

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Abstract
Objective: Clarify the role for postoperative radiation for adenoid cystic carcinoma (ACC) of the head and neck as it relates to tumor site, T‐stage, and surgical margin status.Study Design: Retrospective cohort study at an academic tertiary care hospital.Methods: A review of 129 patients with biopsy‐proven ACC was performed. Previous treatment failures and nonoperative candidates were excluded, with 75 patients considered eligible for further study. Patients were grouped according to treatment modality and Kaplan‐Meier estimates of overall survival, locoregional control, and distant control were compared using log‐rank tests. Patients were also stratified according to tumor site, T‐stage, and surgical margin status, and pair‐wise comparisons of treatment outcome within each group were performed using Wald tests from Cox proportional hazards models.Results: Twenty‐five patients were treated with surgery alone, and 50 were treated with surgery and postoperative radiation. There was no significant difference in outcome between treatment groups when correlated with tumor site (P = .89). However, postoperative radiation was associated with improved overall survival for advanced T‐stage (T4) tumors (P = .019) and greater locoregional control for patients with microscopically positive margins (P = .018). There was no demonstrated benefit of postoperative radiation for patients with microscopically negative margins (P = .93).Conclusions: The findings of this study suggest that advanced T‐stage and positive microscopic margins are important factors in determining the necessity for postoperative radiation therapy for ACC of the head and neck and that radiation therapy may not be necessary for patients with early T‐stage tumors and negative surgical margins.