Epidemiology of neuroendocrine tumors of the appendix in the USA: a population-based national study (2014-2019)

BACKGROUND: The appendix is the third most common place for neuroendocrine tumors (NETs) along the digestive tract and NETs are the most common neoplasms of the appendix. However, there are limited population-based data on the epidemiology of this disease. Using a large database, we sought to describe the epidemiology and risk association of NETs of the appendix. METHOD: We queried a multi-institutional database (Explorys Inc., Cleveland, OH, USA), comprising 360 hospitals in the United States (US), for patients with a diagnosis of NETs of the appendix from 2014-2019. RESULTS: Of the 30,324,050 individuals in the database, 2020 patients had an appendiceal NET diagnosis (0.007%). The most common presenting symptoms included abdominal pain, nausea, vomiting and diarrhea. Patients with appendiceal NETs were more likely to be female (odds ratio [OR] 1.36, 95% confidence interval [CI] 1.24-1.49), Caucasian (OR 2.71, 95%CI 2.40-3.07), with a history of smoking (OR 1.82, 95%CI 1.65-2.01), family history of primary gastrointestinal malignancy (OR 7.26, 95%CI 6.31-8.33), diagnosis of multiple endocrine tumor type 1 (OR 52.31, 95%CI 23.15-118.23), or neurofibromatosis type 1 (OR 16.37, 95%CI 7.24-37.01). CONCLUSIONS: In a population-based study in the US, using the Explorys database, we found the overall prevalence of NETs of the appendix to be 7 per 100,000 persons. The incidence in the year January 2019-January 2020 was 0.4 per 100,000 individuals. These rates are higher than previously reported and may be more accurate, given the more comprehensive nature of the Explorys database.