- Posted December 9, 2025
Agent Orange Linked To Rare Bone Marrow Cancers
Soldiers exposed to the Vietnam War-era defoliant Agent Orange have a higher risk of a rare form of bone marrow cancer, a major new study has found.
The study found that people exposed to Agent Orange face a higher risk of developing myelodysplastic syndrome (MDS), a bone marrow cancer that develops slowly over a lifetime of accumulated genetic damage.
They are also more likely to develop MDS earlier than others and to have more aggressive disease, researchers reported Monday at an American Society of Hematology meeting in Orlando.
“This study has been a personal quest,” said lead researcher Dr. Mikkael Sekeres, chief of hematology at the University of Miami’s Sylvester Comprehensive Cancer Center.
“I see veterans who develop these conditions and need expensive medical care, but I can’t write a letter that establishes causality because, before this study, we hadn’t clearly linked Agent Orange to MDS,” he said in a news release.
About 2.6 million U.S. service members might have been exposed to Agent Orange during the Vietnam War, researchers said in background notes. The defoliant contains one of the most dangerous industrial chemicals ever produced, a toxic form of dioxin.
Previous studies have tied Agent Orange to other blood cancers, including lymphoma, multiple myeloma and leukemia.
But no link between Agent Orange and MDS had been established, mainly because the data weren’t available, Sekeres said.
“No one studied this before because there haven’t been organized registries with the data needed to make this connection," Sekeres said.
MDS affects up to 20,000 Americans each year, typically older than 70, researchers said.
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 enrolled in the study, including 130 who said they’d been exposed to Agent Orange.
Results showed people exposed to Agent Orange tended to be diagnosed with MDS at younger ages.
They also were more likely to have harmful genetic mutations that contribute to MDS, and to exhibit high-risk genetic patterns seen in MDS cases caused by toxic exposure.
“MDS isn’t a one-hit wonder,” Sekeres said. “Patients have one genetic mutation that occurs, then another, then another. It takes decades for those mutations 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 also had twice the risk of their disease progressing after diagnosis. However, overall survival was similar to that of patients not exposed to the defoliant, researchers found.
“The progression finding was surprising,” Sekeres said. “We didn’t expect that signal to be as strong as it was.”
Black veterans were more than twice as likely to be exposed to Agent Orange as white service members, even though they represented just 16% of men who served in Vietnam, researchers said.
“This toxin may have hit a particularly vulnerable population,” Sekeres said.
These results could help veterans receive coverage for treatment of MDS, particularly those exposed to Agent Orange, researchers said.
The team next plans to verify its results using national veteran databases.
“Veterans have been waiting a long time for someone to take this seriously,” Sekeres said. “If our work can move the needle even a little, that feels incredibly meaningful.”
Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
More information
The American Cancer Society has more on myelodysplastic syndrome.
SOURCE: University of Miami, news release, Dec. 8, 2025
