Gen X, millennials showing higher rates of appendix cancer than previous generations
Incidence rates of appendiceal adenocarcinoma were four times higher among individuals born in the late 1980s than in those born in the 1940s at the same point in their lives, a cohort study found.
There has been a sharp increase in appendiceal adenocarcinoma incidence rates in recent generations, particularly Generation X and millennials, according to results of a retrospective cohort study.
To assess incidence rates of appendiceal adenocarcinoma across birth cohorts in the United States, researchers looked at eight population-based cancer registries from the NIH and National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program. The final cohort included 4,858 people who were ages 20 years or older when diagnosed with a pathologically confirmed primary appendiceal adenocarcinoma (1,428 nonmucinous, 1,840 mucinous, 1,273 goblet cell, and 317 signet ring cell carcinoma) between 1975 and 2019. Researchers created 21 overlapping birth cohorts (from 1891–1899 to 1991–1999), then estimated the ratio of age-specific incidence rates in each birth cohort relative to the cohort born in 1941 to 1949 (1945 birth cohort). Findings were published by Annals of Internal Medicine on June 10.
Compared with the 1945 birth cohort, incidence of appendiceal adenocarcinoma was more than triple (incident rate ratio [IRR], 3.41; 95% CI, 2.54 to 4.56) in the 1980 birth cohort and quadruple in the 1985 birth cohort (IRR, 4.62; 95% CI, 3.12 to 6.82). Appendiceal adenocarcinoma rates also increased by about 90% from 1995 to 1999 to 2015 to 2019 (IRR, 1.91; 95% CI, 1.69 to 2.16), for an annual percentage change in age-adjusted incidence rate of 3.71% (95% CI; 3.35% to 4.07%). Age-specific incidence of appendiceal adenocarcinoma increased to varying degrees across successive birth cohorts after 1945 for all tumor histologic types (IRRs, 2.71 [95% CI, 1.73 to 4.26] for mucinous adenocarcinoma, 2.60 [95% CI, 1.46 to 4.63] for nonmucinous adenocarcinoma, and 4.95 [95% CI, 2.77 to 8.85] for goblet cell adenocarcinoma).
Limitations of the study include that the researchers did not investigate birth cohort effects based on sex or race and did not have enough data to look at ultrarare signet ring cell carcinomas.
It's unlikely that the shift from screening sigmoidoscopy to colonoscopy or advances in diagnostic imaging explain the findings, according to the study authors. Overall, the results indicate “there is a timely need for etiologic research as well as increased [appendiceal adenocarcinoma] awareness among providers and the public,” they wrote. “Similar trends have been reported for other gastrointestinal cancers, suggestive of potential shared cause contributing to this increasing cancer burden across generations.”