Survival When Treating Adenoid Cystic Carcinoma of the External Auditory Canal: Quantitative Assessment of Case Reports

Background: Adenoid cystic carcinoma (ACC) of the external auditory canal is a rare neoplastic condition. The purpose of this study was to conduct a quantitative review of case reports to assess the efficacy of treatment options and assess prognostic factors. Methods: Cases were identified using PubMed. Kaplan-Meier curves were used to plot overall and disease-free survival. The log-rank test was used to compare survival curves in the univariate analysis for perineural invasion, margin status, and specific treatment modalities. A Cox proportional hazard model was used for multivariate analysis. Results: Sixty-six cases were identified. The univariate analysis suggests an increased overall (p = .03) and disease-free (p = .03) survival for those treated with parotidectomies, whereas temporal bone resection decreased survival (p = .07). There was no overall or disease-free survival advantage using radiation (p = .8). Positive margins decreased both overall (p = .05) and disease-free survival (p = .02). Perineural invasion was not significant. The multivariate analysis confirmed the findings for parotidectomies (p = .02) and temporal bone resections (p = .01). Conclusions: Although the short-term survival for ACC is high, the risk of metastasis and poor long-term survival is high. In addition to local excision with negative margins, the surgeon should perform a parotidectomy.