(0625) Comprehensive Quantitative Assessment of Malignant Parotid Tumor Incidence Trends Over Three Decades: A Population-Based Study

Introduction: Malignant parotid tumors are rare and represent less than 3% of all head and neck cancers in the United States with an incidence of 0.9 cases per 100,000 people. In this study, we aim to explore the incidence, trends in incidence, presentation, tumor size, and demographics for patients diagnosed with malignant primary parotid tumors from the Rochester Epidemiology Project (REP) from 1990-2022.

Methods: All patients diagnosed with malignant tumors from January 1, 1990, through December 31, 2022, in Olmsted County, Minnesota were identified based on comprehensive individual medical record review using the Rochester Epidemiology Project medical record linkage system. Demographic characteristics, tumor size, clinical presentation, and smoking status were assessed. Trend analysis for incidence, tumor size, and clinical presentation was done using weighted linear regression to correct for differences in number of years per time group (3-5 years).

Results: In total, 57 patients with primary malignant parotid tumors were identified from 1990-2022, 50 of which underwent surgical resection. The average age at diagnosis for included patients was 60.6 years old. The average annual incidence from 1990-2022 was 1.2/100,000 persons/year (0-4.2/100,000 persons/year). The most common malignant tumor in this population was mucoepidermoid carcinoma at 22.8% (13) followed by acinic cell carcinoma 15.8% (9). Tumor size was reported for 50 patients, with an average of 2.7 cm (0.6-6.8 cm). Smoking status was reported in 53 patients. Of the total, 52 patients had reported clinical presentation, with 90.4% (47) of patients presenting with a palpable mass, compared to 9.6% (5) who presented due to incidental imaging findings. Average incidence was overall stable and not statistically significant.

Conclusions: The average incidence of malignant parotid tumors in Olmsted County from 1990-2022 is similar to reported average incidence in the United States. Despite overall stability in incidence over 30 years, variations in tumor types and sizes highlight the need for continued surveillance and research in this patient population.