Appendiceal Cancer in the National Cancer Database: Increasing Frequency, Decreasing Age, and Shifting Histology.

Background: Nonoperative management of acute appendicitis is increasingly common. However, small studies have demonstrated high rates of appendiceal cancer in interval appendectomy specimens. Therefore, we sought to identify national trends in appendiceal cancer incidence and histology.

Study Design: The National Cancer Database was queried for patients 18 years or older, diagnosed with a right-sided colon cancer (including appendiceal) from 2004 to 2017 who had undergone surgery. Outcomes included trends in appendiceal cancer compared with right-sided colon cancers and trends in appendiceal cancer histology. Logistic regression was used to assess trends over time while adjusting for patient age, insurance, income, area of residence, and comorbidity. Predicted probabilities of the outcomes were derived from the logistic regression models.

Results: Of 387,867 patients with right-sided colon cancer, 19,570 had appendiceal cancer and of those 5,628 had a carcinoid tumor. Odds of appendiceal cancer, relative to other right-sided colon cancers, increased from 2004 to 2017 (odds ratio [OR] 2.56, 95% CI 2.35-2.79). The increase occurred in all age groups; however, it was more markedly increased in patients 40-49 years old (2004: 10%, 95% CI 9-12 to 2017: 18%, 95% CI 16-20; pairwise comparisons p < 0.001). Odds of appendiceal carcinoid, relative to other appendiceal histologies, increased from 2004 to 2017 (OR 1.70, 95% CI 1.40-2.07) with the greatest increase in probability of a carcinoid in patients younger than 40 years old (2004: 24%, 95% CI 15-34 to 2017: 45%, 95% CI 37-53; pairwise comparisons p < 0.001).

Conclusion: Appendiceal cancer has increased over time, and the increase appears to be driven by a rise in carcinoids, most prevalent in patients 49 years of age or younger. When nonoperative management of acute appendicitis is undertaken, close follow-up may be appropriate given these findings.