Survival Outcome of Salivary Gland Carcinoma: A 50-Year Retrospective Study With Long-Term Follow-up

Abstract

Salivary gland carcinomas (SGCs) can be classified into more than 20 subtypes with various clinical behaviors. The present study aimed to analyze the clinical and pathological features of SGCs and evaluate their long-term prognosis. A retrospective cohort study was performed. This study investigated cases of histologically confirmed SGC at the authors' institution from January 1963 to December 2014. Data on sex, age, site, histopathological diagnosis, tumor-node-metastasis classification, postoperative radiotherapy and/or chemotherapy, local and regional recurrence, and distant metastasis (DM) were collected as covariates. The overall survival (OS) rate was analyzed as the outcome. Kaplan-Meier survival analysis and Cox multivariate analysis were used for survival analysis. The cohort was divided into 2 groups-before and after 1989. The clinicopathological characteristics of the 2 groups were compared using the χ2 test. The cohort included 1,637 patients who met the admission criteria and had a male-to-female ratio of 0.9:1. The median age was 47years (range, 8months to 86years). The median follow-up time was 54months (range, 1-432months). The majority of the tumors occurred in the parotid gland (35.3%), followed by the palate gland (25.2%). Adenoid cystic carcinoma was the most common tumor type (34.3%), and mucoepidermoid carcinoma (29%) was the second most common type. In the 1,637 patients, the neck lymph node metastasis rate was 8.7% at the first surgery, and the overall DM rate was 14.1%. The 5-, 10-, and 15-year OS rates of the 1,637 cases were 93.1%, 87.2%, and 79.3%, respectively. Comparative analysis before and after 1989 showed statistically significant differences in sex, site, histologic subtype, T classification, local and regional recurrence rate, and radiotherapy (P<.05), while no significant differences were found in age, N classification, M staging, DM, or chemotherapy. The OS rates of SGC have improved significantly over the past 30years. This is attributable to an increase in the proportion of patients diagnosed at the early stage and receiving radiotherapy, as this has led to a reduction in the local and regional recurrence rate and, consequently, an improvement in the survival rates.