Appendiceal cancer — cancer of the appendix — is a rare malignancy that is usually found during surgery for acute appendicitis. Although the rate of appendectomies has been stable over the last two decades, the incidence of malignant appendiceal cancer increased 232% in the United States.
Andreana Holowatyj, PhD, MSCI, and colleagues conducted the first study of appendiceal cancer patterns and survival by race/ethnicity among patients younger than 50 in the U.S.
Reporting in the journal Gastroenterology, they found poorer disease outcomes among non-Hispanic Blacks compared with non-Hispanic whites, and among men compared with women. However, they observed no differences in survival between young Hispanics and non-Hispanic whites with appendiceal cancer.
“Our discovery of disparities in survival across racial/ethnic groups and sex within this patient population noticeably parallels the unequivocal burden of COVID-19 by race or ethnicity and sex,” said Holowatyj, assistant professor of Medicine in the Division of Epidemiology. “These alarming health care realities heighten the need to understand the factors that contribute to disparities in disease susceptibility and prognosis in order to mitigate these differences, particularly for non-Hispanic Black individuals.”
Holowatyj and her colleagues used population-based data from the National Cancer Institute’s SEER program (Surveillance, Epidemiology, and End Results) to compare survival among non-Hispanic whites, non-Hispanic Blacks and Hispanics diagnosed with early-onset appendiceal cancer.
Among 1,652 cases of appendiceal cancer diagnosed in people ages 20 to 49 from 2000-2011, cancer-specific survival 5 years after diagnosis was 77.0% for non-Hispanic whites, 64.5% for non-Hispanic Blacks and 79.2% for Hispanics.
The researchers also uncovered substantial variation in survival depending on the histologic subtype of appendiceal cancer. One-third of young patients were diagnosed with mucinous appendiceal adenocarcinoma, where the most pronounced racial differences in survival were reported between young non-Hispanic Black and non-Hispanic white patients.
The investigators found that socioeconomic status was similar for young non-Hispanic Blacks and Hispanics diagnosed with early onset appendiceal cancer, suggesting that although socioeconomic factors may impact survival rates, they do not completely explain the survival difference between racial/ethnic groups. In ongoing studies, the team aims to determine how health behaviors, environmental exposures, genetics and gene-environment interactions contribute to differences in disease susceptibility and survival.
The researchers are also working to discover risk factors for appendiceal cancer and to define distinct clinical and molecular features of early-onset disease.
“Given the alarming increase in the incidence of appendiceal cancer and the marked disparities among young patients, it’s important to accurately diagnose and distinguish these malignancies,” Holowatyj said. “The potential misclassification of appendiceal cancer as colon cancer is a barrier to discovering disease-specific risk factors and tumor biomarkers, which would have implications for risk assessment, screening, surveillance and treatment.”
With a trend toward non-operative managements of appendicitis, she noted that gastroenterologists and surgeons should keep appendiceal cancer in mind for young patients presenting in this manner.
This research was supported by the National Institutes of Health (grant CA229259), the American Cancer Society and Vanderbilt University Medical Center.
