Clinical Characteristics and Survival in Adenoid Cystic Carcinoma of Salivary and Nonsalivary Sites

OBJECTIVES: Adenoid cystic carcinoma (ACC) typically arises from salivary glands of the head and neck but also occurs in sites outside of the head and neck; however, data regarding nonsalivary ACC are scarce. We present a comparison of the clinical behavior, treatment patterns, and survival outcomes of ACC of salivary and nonsalivary sites using the National Cancer Database (NCDB). METHODS: Retrospective analysis of patients diagnosed with ACC between 2004 and 2020 in NCDB. Patients were identified using the histology code 8200 and categorized by site based on primary site ICD-O-3 codes. Anatomic sites with more than 100 patients were included for analysis. RESULTS: A total of 16,962 patients with ACC from seven sites (major salivary, minor salivary, respiratory, skin, breast, female genital, and eye/orbit) were included in the final analysis. Among all sites, minor salivary gland tumors were most likely to present with locally advanced disease (T3 or T4) while those of the respiratory tract were most likely to present with regional (26%) or distant metastasis (11.1%). On multivariate analysis controlling for age, sex, treatment, T and N classification, only breast primaries had significantly different survival from major salivary primaries (HR 0.59, 95% CI 0.49-0.72). CONCLUSION: The clinical behavior of ACC varies significantly by anatomic primary site. Survival differences between the different anatomic sites appear to be driven largely by differences in the extent of disease at presentation, although patients with breast primaries had significantly better survival than salivary gland primaries even when controlling for these factors.