Demographics, clinical features, and survival of patients with adenoid cystic carcinoma in major and minor salivary glands versus non-salivary sites: an updated SEER analysis

Introduction Adenoid cystic carcinoma (ACC) is a rare malignancy of secretory glands, most commonly arising in the salivary glands but also reported in the lung/bronchus, breast, skin, and other secretory gland tissues. Although typically slow-growing, ACC is also associated with high risk of local recurrence and distant metastases. Population-based studies are necessary to understand site-specific characteristics and clinical outcomes.Materials and methods We analyzed SEER 17 data from 2009 to 2021 to assess site distribution, demographic and clinical characteristics, and survival among patients with ACC. Frequencies were calculated for common sites, and cause-specific survival (CSS) was evaluated by site and stage. Cox regression was used to identify predictors of survival.Results A total of 4,294 ACC cases were identified. The most common sites were the major salivary glands (32%), and the collective sites classified as minor salivary glands (36%), while non-salivary gland sites accounted for 32%, including breast (16%), skin (6%), lung/bronchus (5%), and eye/orbit (2%). This represents a small but significant increase in ACC arising at non-salivary sites compared with pre-2009 SEER data (28%). Five-year CSS was high for localized disease (87-99%), moderate for regional disease (57-92%), and poor for distant disease (12-61%). Older age, high tumor grade, large tumor size, and nodal involvement were associated with worse survival. Stage- and site-specific survival patterns were consistent with earlier SEER data.Conclusions ACC is a heterogeneous cancer with distinct site-specific features. Survival has remained largely unchanged over the past three decades. Poorer outcomes are associated with older age, high tumor grade, larger tumors, and advanced stage.