Date of Award

January 2014

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Benjamin L. Judson

Subject Area(s)

Medicine

Abstract

Parotid carcinomas are rare head and neck cancers with 24 different histologic subtypes. Prognostic factors associated with disease-specific survival (DSS) in the various histologic subtypes of parotid carcinomas are poorly understood. Through three studies, we sought to characterize the demographic, clinical, and pathologic characteristics associated with survival three different parotid carcinomas.

The aim of our first study was to analyze the effect of grade on DSS and the topographical distribution of nodal metastases in mucoepidermoid carcinoma (MEC). We hypothesized that histologic grade influences survival and the distribution of nodal metastases. We identified 2,400 adult patients with MEC in the Surveillance, Epidemiology, and End Results (SEER) database from 1988 to 2009. Bivariate, univariate, and multivariate regression analyses were used. 5-year DSS rates for low, intermediate, and high grade MEC were 98.8%, 97.4%, and 67.0%, respectively (P< .001). Negative prognostic factors included high grade, increasing patient age and tumor size, extraparenchymal extension, nodal metastases, and distant metastases. High grade MEC was more likely to have lymph node metastases in levels I-III (34.0%), than low (3.3%) and intermediate grade MEC (8.1%) (P< .001). Grade influenced the prognosis and distribution of nodal metastases. Results indicated that management guidelines should vary based on grade.

The aim of our second study was to describe the incidence and baseline characteristics of patients with squamous cell carcinoma (SCC) of the parotid and identify prognostic factors associated with DSS. We hypothesized that surgery, adjuvant radiation, and age would be independent predictors of survival. We identified 2,104 adult patients with SCC in the SEER database from 1988 to 2009. χ2, t tests, and multivariate regression were used. SCC is the second most common parotid malignancy, and its incidence is increasing (annual percentage change 1.7%, Ptrend= .004). Age ≥85, tumor size ≥4 cm, extraparenchymal extension, cervical metastases, and distant metastases were independently associated with disease-specific mortality. Compared to no surgery, surgery was associated with improved 5-year DSS (44.4% vs 71.0%, P< .001), while radiation alone was similar to no treatment (47.0% vs 41.6%, P= .28). Surgery and adjuvant RT were associated with improved survival compared to radiation alone and no treatment. Patients ≥85 years of age comprised nearly 20% of all patients and had a poor prognosis independent of treatment.

The aim of our third study was to identify prognostic factors associated with DSS in carcinoma ex pleomorphic adenoma (CXPA). We hypothesized that nodal metastases would be an important prognostic factor associated with DSS. We identified 278 patients with CXPA in the SEER database. χ2, t tests, and multivariate regression were used. Extraparenchymal extension of the primary tumor was associated with positive cervical lymph nodes (35.7% vs 2.9%, P< .001). Independent predictors of DSS were race (hazard ratio [HR], 7.12; 95% confidence interval [CI], 2.56-19.82), distant metastases (HR, 18.99; 95% CI, 5.06-71.21), and the presence of multiple metastatic lymph nodes (HR, 9.48, 95% CI, 4.14-21.71). Patients with multiple cervical lymph node metastases had decreased 5-year DSS compared to patients with ≤1 positive lymph node (42.7% vs 85.9% P< .001). The presence of two or more cervical lymph node metastases identified high-risk CXPA patients with a poor prognosis.

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