The Significance of Close Margins on Outcome of Patients with Adenoid Cystic Carcinoma of the Skull Base: An International Collaborative Study

Background: The mainstay of treatment in adenoid cystic carcinoma (ACC) of the head and neck is surgical resection with negative margins. Surgical resection of skull base ACC might be limited by proximity to vital structures. The clinical significance of close margins (not involved but less than 5 mm) in ACC remains undefined. This study aims to characterize the impact of close margin on the outcome of patients with ACC of the skull base. Methods: Univariate and multivariate models were used to evaluate the clinical and pathologic data in an international collaborative study. Results: A total of 507 patients with ACC of the head and neck were analyzed. Of those, 108 (22%) had ACC of the paranasal sinuses and skull base. Negative margins were achieved in 38 (35%) patients with paranasal sinuses ACC compared with 49% and 57% in patients with major salivary glands and oral cavity ACC, respectively (p = .001). Close margins, were found in 16 patients (15%), with skull base ACC. Univariate analysis revealed that margin status was significant for 5 years overall survival (OS, p = .009) disease specific survival (DSS, p = .003) and disease free survival (DFS, p = .015) for patients with ACC of the skull base. Multivariate analysis in patients with ACC of the skull base, revealed that close margin status was a significant predictors for 5 years OS (HR-2.11, 95% CI, 1.3–4.2, p = .01), DSS (HR-2.1, 95% CI, 1.2–3. 1, p = .03) and DFS (HR-3.1, 95%CI, 1.3–8.2, p = .03). Conclusions: In patients with skull base ACC, close margins should be considered as an adverse pathological feature similar to positive margins.