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Program Number: B319
Session Name: Poster Session

Treatment Patterns and Survival in Mucoepidermoid Carcinoma - An Analysis of the National Cancer Database from 2004-2020

Ameen Amanian, MD, MSE; Naomi Wang, BSc; Alexandria Yao, BA; Maria Feucht, MD; Uma Ramesh, BSc; Andrés Bur, MD; University of Kansas Medical Center

Background: Mucoepidermoid carcinoma (MEC) is one of the most prevalent malignancies affecting the major salivary glands, with histologic grading historically guiding adjuvant treatment decisions post-primary surgical therapy. While adjuvant radiotherapy is commonly recommended for high-grade MEC, intermediate-grade tumors occupy a clinical gray zone. The primary question remains whether intermediate-grade lesions exhibit behavior more akin to low-grade lesions, potentially allowing patients to avoid adjuvant radiotherapy and its associated morbidity. Addressing this question is of critical clinical importance, particularly in light of the forthcoming reclassification by the College of American Pathologists, which will consolidate low- and intermediate-grade cases into a single histologic category.

Methods: The National Cancer Database (NCDB) was queried for patients diagnosed with salivary mucoepidermoid carcinoma between 2004 and 2020. The analysis included anatomic subsites including the parotid, submandibular, sublingual, and minor salivary glands. Baseline demographic comparisons utilized univariate chi-square and independent t-test analyses. Multivariable Cox regression and Kaplan-Meier analyses were conducted to assess 5-year overall survival (OS). 

Results: Among the 6,348 patients included, majority of MEC cases originated in the parotid gland (87.7%, n = 5565), followed by the submandibular gland (7.9%, n = 500). The cohort’s mean age was 54.4 years, with a predominant female representation (58.3%, n = 3700). Low-grade tumors comprised 46.0%, intermediate-grade 39.4%, and high-grade 14.6%. Most low-grade MECs were treated with surgery alone (76.2%), whereas high-grade cases frequently received surgery with adjuvant treatment (75.8%). In the intermediate MEC group, 50.3% (n = 1258) underwent partial gland excision, 34.4% (n = 859) total gland excision, and 2.6% (n = 65) required radical resection. A neck dissection was performed in 40.9% of these cases. Trends over time showed an increase in intermediate-grade MECs treated with surgery alone (2004–2009: 53.3%, 2010–2014: 56.4%, 2015–2020: 57.4%, p = 0.102) (Figure 1). 

Cox proportional hazards modelling showed no significant prognostic difference between low-grade and intermediate-grade MECs (HR: 1.148 [CI: 0.94-1.39], p = 0.165). Notably, tumors originating in the submandibular gland had poorer 5-year OS compared to those in the parotid gland (HR: 1.42, [CI: 1.11-1.81], p = 0.005). Kaplan-Meier analysis demonstrated nearly identical 5-year OS for low- and intermediate-grade MEC, while high-grade MEC showed significantly lower 5-year OS (Figure 2). Stratification of intermediate-grade MEC by treatment type revealed no significant survival difference between those treated with surgery alone versus surgery followed by adjuvant radiotherapy (p=0.913). 

Conclusions: A trend towards de-escalation in the treatment of intermediate-grade MEC has emerged, supported by survival analyses indicating comparable OS between intermediate- and low-grade MEC. Furthermore, adjuvant radiotherapy did not confer a survival benefit in intermediate-grade cases, suggesting biological behavior akin to low-grade MEC. As some institutions have begun reclassifying intermediate-grade as low-grade, a reevaluation of the grading system may be warranted. Future research should continue to investigate the utility of a three-tier grading system in MEC to optimize patient care.

Figure 1. Primary treatment modality stratified by year of diagnosis

Figure 2. Kaplan Meier curve for 5-year overall survival using log-rank test

1 - Low-grade, 2 - Intermediate-grade, 3 - High-grade

 

 

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