2853 - Clinical and Histopathological Predictors of Disease-Free Survival in Mucoepidermoid Carcinoma: A Single Institution Retrospective Analysis

10:45am - 12:00pm PT

Hall F

Screen: 32

POSTER

Presenter(s)

Petria Thompson, MD, PhD - University of California San Francisco, San Francisco, CA

P. S. Thompson¹, S. M. Dufault², J. Fortino¹, A. Witztum¹, A. vanZante³, H. Kang⁴, P. Ha⁵, S. S. Yom¹, and J. W. Chan¹; ¹Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, ²University of California, San Francisco, Department of Epidemiology and Biostatistics, San Francisco, CA, ³Department of Pathology, University of California San Francisco, San Francisco, CA, ⁴Department of Medicine, University of California San Francisco, San Francisco, CA, ⁵Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco, San Francisco, CA

Purpose/Objective(s): Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor, representing 30% of cases. Despite its prevalence, MEC demonstrates variable clinical behavior. Histological grading systems classify tumors as low, intermediate, or high grade based on cellular morphology, mitotic rate, necrosis, and perineural invasion (PNI). However, grading alone may not accurately predict outcomes. This study aims to describe the clinical, histopathological, and treatment characteristics of MEC and identify predictors of disease-free survival (DFS).

Materials/Methods: A retrospective cohort of 231 MEC patients diagnosed between 1990 and 2022 at a single institution was analyzed. Clinical and treatment data were collected, including tumor grade, stage, surgical margins, and adjuvant therapy. Tumor grade was generally assessed using the Brandwein and AFIP systems. In discordant cases, the lower grade was selected for analysis. Disease-free survival (DFS) was evaluated using the Kaplan-Meier method, with statistical significance determined by the log-rank test. Univariate analyses assessed the impact of factors such as stage, tumor grade, perineural invasion (PNI), lymphovascular invasion (LVSI), and tumor site on DFS. A p-value of less than 0.05 was considered statistically significant.

Results: The median follow-up period was 98.7 months (IQR: 53.9-170). Among 231 patients, 58.4% had low-grade tumors, 14.3% intermediate-grade, and 16.5% high-grade. Surgery was performed in all cases, with 37% of patients receiving adjuvant radiation and 5.6% chemotherapy. Positive margins (31.6%), PNI (19.5%), and lymphovascular space invasion (6.1%) were observed. 5-year DFS in the entire cohort was 75%. DFS was significantly worse in univariate analysis for positive margins, PNI, advanced-stage disease (T3-4 and/or node-positive), and higher tumor grade (p<0.05). K-M analysis demonstrated a statistically significant difference in DFS amongst tumor sites (p=0.029). Minor salivary gland MEC showed significantly worse DFS than other site groups (major salivary Gland, other head and neck, non-head and neck).

Conclusion: This study highlights the prognostic impact of margin status, PNI, disease stage, tumor grade, and primary tumor location in MEC. The addition of molecular biomarkers to clinical and histopathological prognostic factors may further improve risk stratification to help personalize treatment strategies.