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Gen X, Millennials Face Higher Risk for Rare Appendix Cancer
The incidence of appendiceal adenocarcinoma in the United States more than tripled among those born in 1980 and rose more than fourfold among those born in 1985 compared with a cohort born in 1945, a study found. Greater recognition of appendix cancer as distinct from colon cancer could partly explain the results, but generational differences in exposures affecting cancer risk are also possible, the researchers said.
METHODOLOGY:
A retrospective cohort study analyzed 4858 cases of pathologically confirmed primary appendiceal adenocarcinoma diagnosed between 1975 and 2019 in patients aged 20 years or older from eight population-based cancer registries in the United States.
Researchers used data from the National Cancer Institute's Surveillance, Epidemiology, and End Results Program to examine age-specific incidence rates across overlapping birth cohorts from 1891 to 1999.
The analysis included four histologic subtypes: Mucinous (1840 cases), nonmucinous (1428 cases), goblet cell adenocarcinomas (1273 cases), and signet ring cell carcinomas (317 cases).
Age-specific incidence rates were calculated per 100,000 persons in 5-year periods from 1975 to 2019, with the 1945 birth cohort serving as the reference group.
TAKEAWAY:
Compared with the 1945 reference cohort, the incidence rate ratio (IRR) for the 1980 birth cohort was 3.41 (95% CI, 2.54-4.56).
For the 1985 cohort, the IRR was 4.62 (95% CI, 3.12-6.82).
Goblet cell adenocarcinomas showed the most pronounced increase among histologic subtypes.
IN PRACTICE:
'Birth cohort effects have also been reported for colon, rectal, and gastric cancer, suggesting that both shared and distinct risk factors may contribute to gastrointestinal carcinogenesis,' the researchers wrote. 'These results support the need for histology-specific investigations of appendiceal adenocarcinoma, as well as increased education and awareness of appendiceal adenocarcinomas among healthcare providers and the public.'
SOURCE:
Andreana N. Holowatyj, PhD, with Vanderbilt University School of Medicine, in Nashville, Tennessee, was the corresponding author of the study, which was published online on June 10 in Annals of Internal Medicine .
LIMITATIONS:
Appendix cancer had been treated as colon cancer until relatively recently, the researchers noted. But the increase in goblet cell carcinomas, which typically only occur in the appendix, 'suggests that misclassification of appendiceal versus colon cancer is unlikely to explain our findings,' Holowatyj's group wrote.
DISCLOSURES:
The study was supported by grants from the Appendix Cancer Pseudomyxoma Peritonei Research Foundation and the National Institutes of Health.
