The clinical outcomes and overall survival in patients with mucoepidermoid and adenoid cystic carcinoma of the salivary glands: A comparative analysis of long-term outcomes

PURPOSE: Mucoepidermoid carcinoma (MEC) and adenoid cystic carcinoma (AdCC) are the two most common salivary gland malignancies, but differ substantially in biological behavior, recurrence patterns and long-term prognosis. Comparative data from patients treated within the same institution using similar management strategies remain limited. This study compared long-term survival, recurrence patterns and prognostic factors between MEC and AdCC to identify histology-specific characteristics that may inform follow-up and treatment strategies. METHODS: We performed a retrospective cohort study of patients treated for MEC or AdCC at a tertiary academic center between 1996 and 2022. Primary outcomes were overall survival (OS), disease-free survival (DFS) and recurrence patterns, analyzed using Kaplan-Meier curves and multivariable Cox regression. RESULTS: Sixty-two patients (31 AdCC, 31 MEC) were included. Although 5-year OS was identical (81%), AdCC had significantly poorer DFS (53% vs. 80%, p = 0.015) and higher recurrence rates (18/31 vs. 8/31, p = 0.020), and more distant metastases (18/31 vs. 1/31 patients, p = 0.0016). High tumor grade, defined according to tumor-specific pathological criteria, was the strongest independent predictor of poor outcomes (OS: HR = 19.72, p < 0.001; DFS: HR = 3.99, p = 0.01). Advanced T stage, nodal involvement, and metastatic disease independently predicted worse OS. Seven of 11 patients with locoregional recurrence developed a second recurrence, predominantly in AdCC. Curative-intent salvage therapy did not improve OS. CONCLUSIONS: Tumor grade is the strongest prognostic determinant, surpassing histologic subtype. AdCC demonstrates more aggressive biology with higher recurrence rates and poorer DFS despite similar OS. The limited survival benefit of salvage therapy highlights the need for grade-adapted management and more effective therapies for high-grade disease.