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Peritoneal Surface Malignancies

E350: Increasing Incidence of Appendiceal Cancers in the United States

Introduction: Appendiceal cancer is rare and includes several subtypes. We sought to determine appendiceal cancer incidence trends.

Methods: Observational population-based data were extracted from the NPCR-SEER United States Cancer Statistics (USCS) Database for the years 2001-2020; annual percentage change (APC) in rates were calculated using the least-squares method.

Results: Across the 20-year study period, incidence rates of appendix cancer dramatically increased (APC +7.5%; 95% CI 6.5 to 8.5%) while cancers of the colon (APC -2.9%; 95% CI -3.1% to -2.7%) or rectum (APC -1.8%; 95% CI -2.4 to -1.5%) decreased. In 2020, reported incidence of appendix, colon, and rectal cancers were lower all than expected (by 400, 10300, and 5900 cases respectively) suggesting COVID-19 related missed diagnoses. Among cancers arising in the appendix, neuroendocrine tumors had the greatest rate increase (APC +19.9%) although adenocarcinoma (APC +3.2%), goblet cell (APC +4.7%), and mucinous adenocarcinoma (APC +1.9%) also rose; there were no changes in signet adenocarcinomas or lymphoma.  Newly diagnosed appendix cancers rose from 1,570 in 2001 to 6,549 in 2019 (1.7 cases per 100,000 person-years) including ~3000 neuroendocrine cancers, 1100 mucinous adenocarcinomas, 1000 goblet cells, 1000 adenocarcinoma NOS, and 170 signets. Appendix cancer now accounts for 5.2% of all colorectal cancers. Neuroendocrine cancers represented 95% of pediatric cases. Extent of disease varied greatly by subtype, with 62% of signet adenocarcinomas, 56% of mucinous adenocarcinomas, and 29.7% of adenocarcinoma NOS presenting with distant metastatic disease as compared to only 16.7% of goblet cell cases and 3.4% of neuroendocrine (p< 0.05).

Conclusions: Appendix cancer reported incidence is dramatically increasing in contrast to other colorectal cancers. Appendiceal adenocarcinomas frequently present with metastatic spread. As the impact of appendiceal cancer increases, improving clinical awareness of diagnosis and management will be essential for optimizing patient care.

Learning Objectives:

  • Upon completion, participant will be able to list different types of appendiceal cancers.
  • Upon completion, participant will be able to describe how the incidence of appendiceal cancer has increased over the past 20 years in comparison to colon and rectal cancer.
  • Upon completion, participant will be able to describe how the COVID-19 pandemic may have affected the incidence and diagnosis of appendiceal, colon, and rectal cancers.