A population-based analysis of adenosquamous carcinoma of the salivary gland.

Background: Adenosquamous carcinoma (ASC) of the salivary gland is a rare malignancy, and the characteristics and prognosis of this disease remain unclear. This study aimed to assess the clinicopathological characteristics of this rare disease and further determine the potential prognostic factors that affect its outcome.

Methods: Data of patients with ASC of the salivary gland were extracted retrospectively from the Surveillance, Epidemiology, and End Results (SEER) database between 1973 and 2016. The clinicopathological characteristics of these patients were assessed, and prognostic factors were further determined using Cox regression analysis.

Results: A total of 106 patients with ASC of the salivary gland were identified. The mean age at diagnosis was 66.1±14.9 years, with a male-to-female ratio of 1.47. The parotid gland was the most common primary site (N=91; 85.8%). The 1-, 2-, and 5-year overall survival (OS) rates were 71.5%, 55.0%, 41.5%, respectively. The 1-, 2-, and 5-year disease-specific survival (DSS) rates were 80.8%, 72.2%, and 59.2%, respectively. The OS and DSS shortened with increasing tumor stage, regardless of the American Joint Committee on Cancer tumor-node-metastasis stage or SEER historic stage. Surgery was the main treatment option to improve survival, and post-operative radiotherapy could also prolong OS and DSS (both P<0.01). A multivariate Cox regression analysis demonstrated that distant metastases and the use of surgery or radiation were independent prognostic factors for a favorable OS among patients with ASC of the salivary gland, and early stage (T1/T2) and the use of surgery were independent prognostic factors for favorable DSS among the patients with ASC of the salivary gland.

Conclusions: This is the largest case series on ASC of the salivary gland. Advanced T stage, distant metastases, and the use of surgery and radiation were associated with OS or DSS of this disease.