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Epidemiology, Prognostic Factors, and Treatment of Malignant Submandibular Gland Tumors: A Population-Based Cohort Analysis.

IMPORTANCE
Malignant tumors of the submandibular gland are uncommon, leading to limited information regarding prognostic factors and difficulty in evaluating treatment modalities.


OBJECTIVE
To investigate the correlates of survival in patients with primary malignant tumors of the submandibular gland.


DESIGN, SETTING, AND PARTICIPANTS
Data from 2626 patients with a diagnosis of primary tumors of the submandibular gland between 1973 and 2011 in the Surveillance, Epidemiology, and End Results database were used in a retrospective population-based cohort analysis. Kaplan-Meier analysis along with multivariate Cox regression analysis was performed to determine prognostic factors in overall survival (OS) and disease-specific survival (DSS).


INTERVENTIONS
Patients were treated with surgery, radiation therapy, both, or neither.


MAIN OUTCOMES AND MEASURES
Overall and disease-specific survival.


RESULTS
We identified 2626 patients with a diagnosis of primary malignant tumors of the submandibular gland, 52.9% male and 47.1% female, with a mean (range) age of 61.3 (7-101) years. Adenoid cystic carcinoma (36.0%) was the most prevalent histologic subtype, followed by squamous cell carcinoma (18.1%), mucoepidermoid carcinoma (16.9%), and adenocarcinoma (13.7%). Kaplan-Meier analysis demonstrated an OS and DSS of 65% and 74%at 2 years, 54% and 67% at 5 years, and 40% and 60% at 10 years, respectively. Multivariate Cox regression analysis revealed independent predictors of OS and DSS to be age (HR, 1.04 [95% CI, 1.03-1.04], P < .001; HR, 1.02 [95% CI, 1.01-1.03], P < .001), sex (HR, 0.69 [95% CI, 0.57-0.84], P < .001; HR, 0.73 [95% CI, 0.56-0.96], P = .02), tumor grade (HR, 1.47 [95% CI, 1.19-1.81], P < .001; HR, 1.67 [95% CI, 1.25-2.25], P = .001), stage at presentation (HR, 1.56 [95% CI, 1.41-1.72], P < .001; HR, 1.96 [95% CI, 1.69-2.28], P < .001), and surgical resection (HR, 0.55 [95% CI, 0.41-0.74], P < .001; HR, 0.51 [95% CI, 0.35-0.75], P = .001).


CONCLUSIONS AND RELEVANCE
We report, to our knowledge, the largest study to date focused on correlates of survival in submandibular gland malignant neoplasms. Multivariate analysis found that older age at diagnosis, high tumor grade, and later stage at presentation were correlated with decreased survival whereas female sex and surgical resection were correlated with increased survival. In addition, a 3-cm tumor cutoff size was demonstrated above which was associated with a significantly less favorable prognosis. Radiation therapy had mixed association with survival, dependent on tumor size and subtype.