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Research Original Investigation

Epidemiology and Treatment of Malignant Submandibular Gland Tumors

Table 4. Multivariate Cox Regression Analysis Stratified by Histologic Subtype

Overall Survival

Disease-Specific Survival

Characteristic

HR (95% CI)

P Value

HR (95% CI)

P Value

Squamous Cell Carcinoma Age

1.03 (1.01-1.04) 0.95 (0.66-1.37) 1.17 (0.89-1.55) 0.87 (0.62-1.23) 1.25 (1.01-1.56) 0.83 (0.52-1.33) 0.94 (0.66-1.36) 1.03 (1.02-1.05) 0.52 (0.30-0.91) 0.96 (0.74-1.25) 1.87 (1.10-3.16) 1.63 (1.29-2.08) 0.41 (0.21-0.81) 0.60 (0.37-0.96) 1.05 (1.03-1.07) 0.83 (0.47-1.46) 1.31 (0.92-1.86) 2.96 (1.74-5.04) 2.04 (1.54-2.69) 0.32 (0.07-1.58) 0.69 (0.37-1.27) 1.04 (1.02-1.06) 0.73 (0.46-1.17) 0.71 (0.50-1.01) 1.89 (1.11-3.19) 1.21 (0.98-1.50) 0.52 (0.22-1.19) 1.78 (1.05-3.03)

.001

1.01 (0.99-1.03) 0.88 (0.52-1.47) 1.08 (0.76-1.54) 0.87 (0.54-1.39) 1.58 (1.12-2.22) 0.76 (0.42-1.40) 0.87 (0.51-1.47) 1.00 (0.97-1.02) 0.34 (0.13-0.90) 0.94 (0.67-1.33) 2.10 (0.92-4.81) 2.73 (1.69-4.43) 0.26 (0.10-0.64) 0.45 (0.22-0.90) 1.03 (1.00-1.05) 0.81 (0.41-1.63) 1.32 (0.89-1.98) 3.63 (1.88-7.02) 2.03 (1.44-2.85) 0.36 (0.06-2.02) 1.40 (0.60-3.25) 1.03 (1.00-1.05) 0.76 (0.39-1.48) 0.60 (0.34-1.04) 2.06 (0.98-4.36) 1.43 (1.04-1.97) 0.21 (0.07-0.58) 4.34 (1.67-11.32)

.24 .65 .66 .55

Sex

.80 .27 .44 .04 .44 .75

Race

Grade

Stage at presentation

.009

Surgery

.38 .59

Radiation therapy Adenocarcinoma Age

<.001

.77 .03 .74 .08

Sex

.02 .77 .02

Race

Grade

Stage at presentation

<.001

<.001

Surgery

.01 .03

.004

Radiation therapy

.02

Adenoid Cystic Carcinoma Age

<.001

.03 .56 .19

Sex

.52 .13

Race

Grade

<.001 <.001

<.001 <.001

Stage at presentation

Surgery

.16 .23

.25 .43

Radiation therapy

Mucoepidermoid Carcinoma Age

<.001

.02 .42 .07 .06 .03

Sex

.19 .06 .02 .08 .12 .03

Race

Grade

Stage at presentation

Surgery

.003 .003

Radiation therapy

Abbreviation: HR, hazard ratio.

squamous cell carcinoma. The most common malignant his- tologic tumor subtype reported in this studywas adenoid cys- tic carcinoma (36.0%) (Table 1), whichmatches what has been reported inprevious studies. 32,37,38 Primary squamous cell car- cinomawas reported in this database at ahigher frequency than expected. This may be due to the difficulty in distinguishing betweenmetastatic squamous cell carcinoma to the subman- dibular gland, primarymucoepidermoid tumors, and true pri- mary squamous cell carcinoma, which may have led to some misclassification of tumor types. 2 We also report the inci- dence of mucoepidermoid carcinoma to be 16.9%, which is similar to what has been reported in other studies. 5,12,32,38,39 The incidence of adenocarcinoma in the patientswhomwe re- viewed (13.7%) matcheswhat has been reported in some stud- ies but is higher comparedwith other studies. 32,38,39 Adenoid cystic carcinomademonstrated the bestmedianOS (12.1 years), whereas squamous cell carcinoma exhibited the lowest (1.9 years), matching what has been reported in the literature. 2 AnalysisofsurvivaldatafromtheSEERdatabaseshowedthat largertumorsizeandadvancedtumorstageatpresentationwere associatedwithadecrease inmedianOS. Kaplan-Meier survival

bidities, extent of surgical resection,margin status, and admin- istration of chemotherapy as a treatment regimen. This limita- tion ofmissing chemotherapy data is likely not problematic for this study on submandibular gland tumors because chemo- therapy has not been shown to be effective in the treatment of salivary gland cancer and has been recommended for use only in recurrence, palliative care, and rapidlyprogressive disease. 16 Furthermore, there are concerns of tumormisclassificationbe- cause there is a lack of centralized review by a head and neck pathologist. This study represents, to our knowledge, the largest popu- lation-based analysis of prognostic factors for survival in pa- tients with tumors of the submandibular gland, including analysis basedon tumor stage, size, and type. The large sample size of this study allowed for the comparisonof survival among several primary histologic tumor subtypeswithin the subman- dibular gland. However, because of the rarity of some of these histologic subtypes leading to an inadequate number of cases for sufficient statistical power, median survival andmultivar- iate analysis were calculated only for primary adenoid cystic carcinoma, adenocarcinoma,mucoepidermoidcarcinoma, and

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