TUESDAY, Dec. 9, 2025 (HealthDay News) — Soldiers exposed to the Vietnam War-era defoliant Agent Orange are at increased risk of a rare form of bone marrow cancer, a large new study finds.
The study found that people exposed to Agent Orange have an increased risk of developing myelodysplastic syndrome (MDS), a bone marrow cancer that develops slowly over a lifetime due to accumulated genetic damage.
They are also more likely to develop MDS earlier than others and to have more aggressive disease, researchers reported Monday at a meeting of the American Society of Hematology in Orlando.
“This study was a personal endeavor,” said lead researcher Dr. Mikkael Sekeres, chief of hematology at the University of Miami Sylvester Comprehensive Cancer Center.
“I see veterans developing these conditions and requiring expensive medical care, but I cannot write a letter establishing causality because we did not have a clear link between Agent Orange and MDS before this study,” he said in a press release.
About 2.6 million U.S. soldiers may have been exposed to Agent Orange during the Vietnam War, researchers said in background information. Defoliant contains one of the most dangerous industrial chemicals ever created: a toxic form of dioxin.
Previous studies have linked Agent Orange to other blood cancers, including lymphoma, multiple myeloma and leukemia.
However, no connection has been established between Agent Orange and the MDS, mainly because the data is not available, Sekeres said.
“Nobody had investigated this before because there were no organized records with the data needed to make this connection,” Sekeres said.
According to the researchers, MDS affects up to 20,000 Americans each year, typically over the age of 70.
For this new study, researchers analyzed data from a federally funded study that enrolled patients with suspected or diagnosed MDS between 2016 and 2024.
Researchers focused on 2,115 people who took part in the study, including 130 who reported exposure to Agent Orange.
The results showed that people exposed to Agent Orange tended to be diagnosed with MDS at a younger age.
They were also more likely to carry deleterious genetic mutations that contribute to MDS and to have high-risk genetic patterns that occur in MDS due to toxic exposure.
“MDS is not a one-time success,” Sekeres said. “Patients experience one genetic mutation, then another, and then another. These mutations take decades to develop, and with an exposure like Agent Orange, patients can acquire that first mutation at a younger age than they normally would.”
MDS patients exposed to Agent Orange were also twice as likely to have their disease progress after diagnosis. However, researchers found that overall survival was similar to that of patients who were not exposed to the defoliant.
“The finding of progression was surprising,” Sekeres said. “We didn’t expect the signal to be as strong as it was.”
According to the researchers, black veterans were more than twice as likely to be exposed to Agent Orange as white service members, even though they made up only 16% of the men who served in Vietnam.
“This toxin may have affected a particularly vulnerable population,” Sekeres said.
These findings could help veterans obtain coverage for MDS treatment, particularly those who have been exposed to Agent Orange, according to the researchers.
The team plans to next validate its findings using national veterans databases.
“Veterans have waited a long time for someone to take this seriously,” Sekeres said. “If our work can move the needle even a little bit, that has incredible significance.”
Results presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
More information
The American Cancer Society has more information about myelodysplastic syndrome.
SOURCE: University of Miami press release, December 8, 2025
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