WASHINGTON, DC — For a half-century, Vietnam veterans have been assumed to have a greater risk of dying of cholangiocarcinoma (CCA), a form of bile duct cancer. A new study suggested that might not be the case, however.
“A variety of risk factors potentially related to Vietnam deployment may be associated with an increased risk of mortality from CCA,” explained researchers from the VHA’s Epidemiology Program, Health Outcomes Military Exposures (HOME) epidemiology program. Their study was the first to assess the risk of CCA mortality among all Vietnam War-era veterans.
Published in Cancer Epidemiology, the Vietnam Era Veterans Mortality Study is a retrospective mortality study of all 2.5 million veterans who served in Vietnam and Southeast Asia (theater) and the 7.3 million veterans who served elsewhere during the Vietnam War (nontheater). The researchers tracked mortality from 1979 to 2019.1
Hazard ratios (HRs) calculated from Cox proportional hazards models, adjusted for sex and age, compared CCA mortality risk between theater and nontheater veterans overall and by branch of service. The researchers also compared branch specific crude rates of CCA between theater and nontheater veterans.
Overall, 2,410 and 6,502 CCA deaths among all theater and nontheater veterans occurred respectively. No increased CCA mortality risk among theater vs, nontheater veterans was detected after adjusting for sex and age hazard ratio, (HR: 1.00, 95 % CI: 0.95-1.04), however.
“When stratified by branch, the crude HRs for CCA were no different between branch-theater status groups except in non-theater Marines who had lower risk,” the authors advised. “A monotonic increase in crude rates for CCA mortality was observed in both theater and non-theater over forty years of follow-up.”
The study team called the lack of increased risk of CCA mortality in theater vs. nontheater U.S. Vietnam War veterans “an important and new finding.”
Certain exposures during deployment to the 1961-1975 Vietnam War theater of operations had been suspected of leading to higher CCA rates. One was liver flukes; some Vietnam War veterans who ate raw or undercooked freshwater fish during their service may have been exposed to the parasitic worms that can lead to CCA. But the study did not show that.
“Additional research is methodologically difficult, as there is no source of exposure, healthcare, or outcome data for all members of the Vietnam era population,’ the researchers concluded. “However, finding no difference in CCA mortality in the U.S. Vietnam era veteran population by theater status addresses concerns and clarifies that research designs that include data allowing for analysis of known risk factors may help further explain the CCA risk in Vietnam War veterans.”
- Bullman T, Culpepper WJ, Cypel YS, Akhtar F, Morley SW, Schneiderman A, Weitlauf JC, Garges E, Davey VJ. Cholangiocarcinoma (CCA) mortality in Vietnam war era veterans. Cancer Epidemiol. 2025 Feb;94:102721. doi: 10.1016/j.canep.2024.102721. Epub 2024 Dec 9. PMID: 39657421.
