ASH 2025: Study connects Agent Orange exposure to earlier and more severe cases of myelodysplastic syndrome

(Press-News.org) MIAMI, FLORIDA (EMBARGOED UNTIL DEC. 8, 2025, AT 6 P.M. EST) – A new national study shows for the first time that people exposed to Agent Orange face a higher risk of developing myelodysplastic syndrome (MDS), tend to develop it earlier, and often have more aggressive disease that is more likely to progress to acute myeloid leukemia. The study was co-led by researchers at Sylvester Comprehensive Cancer Center, part of the University of Miami Miller School of Medicine.

Many veterans and doctors have long questioned whether Agent Orange exposure during the Vietnam War contributed to cases of MDS, a type of blood cancer. The contaminated chemical is linked to several cancers, but a link to MDS was unclear. This created real barriers for exposed veterans with MDS who are seeking care and disability benefits.

“This study has been a personal quest,” said Mikkael Sekeres, M.D., chief of hematology at Sylvester. “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.”

Sekeres will present the full analysis in a poster presentation Dec. 8, at the 2025 American Society of Hematology (ASH) annual meeting in Orlando.

MDS is a bone marrow cancer that develops slowly over a lifetime of accumulated genetic mutations. MDS affects up to 20,000 Americans each year, typically over 70. Some aggressive cases of MDS eventually progress to acute myeloid leukemia.

“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.”

About 2.6 million U.S. service members may have been exposed to Agent Orange during the Vietnam War. The U.S. government used this chemical as a defoliant, but it accidentally contained one of the most dangerous industrial chemicals ever produced, a toxic form of dioxin. Research already links Agent Orange exposure to blood cancers, including types of lymphoma, multiple myeloma and leukemia.

Studies had not clearly shown a link between Agent Orange exposure and MDS mainly because data were unavailable. “No one studied this before because there haven’t been organized registries with the data needed to make this connection," Sekeres said. Only one older study attempted to explore a possible connection, but it lacked diagnostic confirmation and had incomplete exposure data.

That data gap has caused veterans to go unrecognized for their disease. This new analysis represents the first nationwide, prospective effort able to connect confirmed MDS diagnoses with documented Agent Orange exposure.

The data used in the study come from the MDS Natural History Study, which includes genetic information from bone marrow and data on environmental exposures. The research team examined data from 2,115 people, 130 of whom self-reported Agent Orange exposure. 

The study found that, compared to those who had no exposure, people exposed to Agent Orange were diagnosed with MDS at younger ages. They also had a higher burden of harmful mutations and were more likely to exhibit high-risk genetic patterns seen in toxin-related MDS cases.

Clinically, people exposed to Agent Orange were nearly twice as likely to see their disease progress within the first two years after diagnosis. Thankfully, overall survival between the two groups was similar. “The progression finding was surprising,” said Sekeres. “We didn’t expect that signal to be as strong as it was.”

Across every analysis, the results aligned: exposed patients were younger at diagnosis, had more mutations, faced higher-risk disease and were more likely to progress early. “It’s a consistent signal across the different areas where we look — age of onset, genetics, progression,” Sekeres said.

Veterans who self-reported Agent Orange exposure were significantly more likely to be Black, at rates higher than those seen in Vietnam service demographics. “This toxin may have hit a particularly vulnerable population,” Sekeres said. Importantly, he noted, the data showed no connection between these patterns and smoking — a potential confounding factor. 

For veterans, these results may aid future efforts to improve recognition, screening and access to care. Without official acknowledgment of this link, patients with MDS have struggled to qualify for service-connected benefits. The findings should also prompt clinicians to ask about environmental and military exposures, especially when MDS occurs at a younger age.

The team is preparing follow-up analyses using national veteran databases to strengthen and refine the results. For Sekeres, the goal is simple: ensure that veterans with MDS receive the care they need.

“Veterans have been waiting a long time for someone to take this seriously,” he said. “If our work can move the needle even a little, that feels incredibly meaningful.”

about Sylvester research on the InventUM blog and follow @SylvesterCancer on X for the latest news on its research and care.

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Poster Title: Exposure to agent orange and risk of myelodysplastic syndromes

Date, Time and Location: Dec. 8, 6-8PM; OCCC – West Halls B3-B4

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