Epidemiology of and Prognostic Factors for Appendiceal Carcinomas: a Retrospective, Population-based Study

Background: The aim of this study is to evaluate the epidemiology of and prognostic factors for appendiceal carcinomas (ACs).

Methods: All cases of ACs registered in the Surveillance, Epidemiology, and End Results (SEER) database from 1973 to 2014 were retrospectively identified in this study. Age-adjusted incidence and survival rates were calculated.

Results: We analyzed 7170 patients with ACs. We observed a significant increase in the reported annual age-adjusted incidence of ACs from 1973 (0.18/100,000) to 2014 (1.11/100,000). The elevation of the incidence was noted in all the histological types, stages, and grades. The most common histological type varied by race, with the appendiceal mucinous adenocarcinoma (AMA) being the most common in white, Asian/Pacific Islander, and American Indian/Alaskan Native patients, and the appendiceal adenocarcinoma (AA) being the most common in African American patients. In multivariate analysis of patients with all ACs, gender (P < 0.001), year of diagnosis (P < 0.001), age (P < 0.001), race (P < 0.001), tumor grade (P < 0.001), disease stage (P < 0.001), retrieved regional lymph nodes (P < 0.001), type of surgery performed (P = 0.002), and histologic subtype (P < 0.001) were predictors of outcome. Survival time for all ACs increased from the 1973-1993 period to the 1994-2014 period (HR 0.76; 95% CI, 0.69 to 0.85). Additionally, the 5-year survival rates were 88% for malignant carcinoid, 70% for goblet cell carcinoid, 51% for colonic type adenocarcinoma, 59% for mucinous adenocarcinoma, and 25% for signet ring cell type.

Conclusions: We observed increased reported incidence of ACs and increased survival durations over time, suggesting that clinicians pay more attention to ACs and mastering the characteristic of these tumors.