Alan Eller has spent more than a decade trying to convince the Department of Veterans Affairs that his bladder cancer was the result of exposure to Agent Orange almost 50 years ago in Vietnam.

The Army vet has filed three claims with the agency, most recently in 2014, since a doctor told him the cancer was likely tied to the toxic herbicide.

Each time, even as he found additional doctors to vouch for the link between his cancer and his service, the VA rejected Eller’s claim, arguing there was no proof.

But a report last month by a prominent committee of scientists said there’s now research suggesting otherwise. As a result, the VA is studying whether it should reverse its position and add the condition to the list of illnesses it presumes to be linked to Agent Orange, which the U.S. sprayed across Vietnam during the war.

The VA has no legal obligation to do this and has previously declined to cover other conditions despite research supporting a connection. But if it does this time, the shift could mean thousands of dollars a year for some vets, and even more for those like Eller, who filed claims years ago. In such cases, the agency is required to pay disability benefits retroactively, dating back to the day a veteran first applied.

Eller, a retired welder from Indiana, could receive up to 13 years of back payments. Depending on how severe the VA rated his disability, that lump sum could reach six figures.

“I’ll believe it when I see it,” said Eller, 69, who recalled nights in Vietnam spent sleeping in shallow tidal water that he believes was doused with Agent Orange. “I don’t have a lot of confidence in the VA.”

The VA began its review last month, following the release of findings by the Institute of Medicine, part of the National Academies of Sciences, Engineering and Medicine. A panel of VA scientists and health experts is studying the report to recommend whether the government should begin providing disability benefits to thousands more veterans exposed to Agent Orange who suffer from bladder cancer, under-active thyroid, Parkinson’s-like symptoms or high blood pressure.

Those ailments aren’t currently on the VA’s Agent Orange presumptive list, but the Institute of Medicine found evidence of a link for each of them. A final decision could come by late summer, VA officials said.

“My doctors have been telling me Agent Orange probably caused the cancer dating back almost 20 years now,” said Eller, who was first diagnosed in 1996. “It’s been a fight at every turn with the VA, and now, after all these years, they say maybe there’s something there. I guess better late than never.”

Eller is one of about 5,000 veterans and family members who’ve shared their Agent Orange exposure stories with ProPublica and The Virginian-Pilot over the past several months. More than 125 of them said they’ve been diagnosed with bladder cancer. Hundreds more reported having one or more of the other conditions being reviewed by the VA.

For many of them, having their illnesses added to the VA’s list could end years of struggle to convince the federal bureaucracy they were harmed by their service and deserve to be compensated.

From 1965 to 1970, some 2.6 million U.S. service members were potentially exposed to Agent Orange, which contained an unusually dangerous strand of the chemical dioxin. Since 1991, the VA has granted disability benefits to vets who become ill with one of more than a dozen conditions the agency has deemed connected to Agent Orange, so long as they can prove they served on the ground in Vietnam or on its rivers. Navy vets who served at sea are not considered eligible unless they came ashore or crossed into inland waters.

The new evidence linking Agent Orange to bladder cancer demonstrates how much work remains to understand its effects on vets, said Kenneth Ramos, chairman of the Institute of Medicine committee and an associate vice president at University of Arizona Health Sciences. For years, the committee had concluded the evidence suggested no connection to bladder cancer. But Ramos and his colleagues changed their stance after reviewing a 2014 study that found Korean veterans who were exposed to Agent Orange while serving in Vietnam were twice as likely to die of bladder cancer as vets who weren’t exposed.

It’s not clear how many Vietnam veterans have suffered from bladder cancer, which is the fourth-most common cancer among men in the U.S. In a recent one-year period, the VA said it provided medical care to nearly 5,500 Vietnam vets with the disease, though that isn’t a complete accounting since many vets received medical care outside the VA. It also doesn’t count those who were treated successfully in earlier years and have no further signs of the cancer.

To receive disability payments from the VA for conditions not on its Agent Orange list, a Vietnam veteran must produce evidence, such as a doctor’s opinion, proving that the illness was as likely as not connected to his service. As of last month, only 44 vets had persuaded the VA to compensate them for bladder cancer related to their Agent Orange exposure, sometimes after years of appeals. Many more have been denied.

Brian Sweeney, a Marine Corps veteran in Raleigh, North Carolina, grew emotional after a reporter read details of the new bladder cancer research to him over the phone. Sweeney drove supply convoys out of Da Nang, a port city that served as a major base of operations for the U.S. military. He recalled once driving through a misty fog of chemicals so thick he had to stop the vehicle and turn around.

“I didn’t know it at the time, but that was probably Agent Orange,” Sweeney said.

His mind flashed back to the moment three years ago when he was diagnosed with two cancerous growths in his bladder. He subsequently went to the VA to see if he could receive benefits. The claims specialist “pretty much told me I wasn’t eligible because Agent Orange doesn’t cause bladder cancer,” Sweeney recalled.

He filed a claim with the VA anyway. It’s been three years, and he still hasn’t received a final ruling. After a couple of surgeries and a monthly regimen of immunotherapy, Sweeney is in remission, but he still has to check in with a doctor every few months. The latest Institute of Medicine report feels like vindication, he said.

“There are too many layers and too many unknown faces at the VA,” said Sweeney, a 70-year-old counselor.

Chuck Logan, 73, a Minnesota author who served as an Army field radio operator from 1968 to 1969, was assigned to a district that abutted the southern part of the demilitarized zone, where he said no vegetation was allowed to grow. “I walked around, slept or spent the night in probably the most defoliated patch of the Earth,” he said.

Logan was diagnosed with bladder cancer in 2014 following a life insurance physical that flagged abnormalities with his urine sample. He’s undergoing his fourth round of chemotherapy but “they’re slowly zeroing in on telling me, ‘You better get ready to lose your bladder.’”

The VA’s policy, he said, doesn’t make sense because it provides benefits to Vietnam vets with prostate cancer based on their Agent Orange exposure, but not those with bladder cancer. “If I had cancer a muscle wall away in my prostate, then I would have a 100 percent disability rating. But since it’s in my bladder, it’s totally different.”

Even with the new research, there’s no guarantee the VA will begin compensating vets for bladder cancer or any other condition newly linked to Agent Orange. Since 2007, the Institute of Medicine has flagged evidence that Agent Orange exposure could cause or worsen hypertension, better known as high blood pressure, which affects a third of adults in the U.S. But the VA has repeatedly declined to add the condition, saying that the research isn’t strong enough.

The agency also has declined to act on research suggesting that Agent Orange exposure could lead to increased risk of stroke.

Rick Weidman, the legislative director of Vietnam Veterans of America, believes those decisions are budget-driven rather than science-based: “They like to say, ‘The science isn’t there,’” Weidman said. “But even when the science is there and sitting right in front of them, they still don’t do the right thing.”

Still, adding new conditions to the Agent Orange presumptive list wouldn’t be unprecedented. In 2010, prompted by the Institute of Medicine, the VA added three: Parkinson’s disease, ischemic heart disease and a certain type of leukemia.

The additions led to thousands of new claims, contributing to a backlog that took the VA years to recover from. It also forced the agency to re-review about 150,000 previously denied claims – a process now under scrutiny by the House Committee on Veterans Affairs. A whistleblower claimed that a VA contractor rushed through reviews to maximize profit over accuracy and possibly blocked tens of thousands of veterans from benefits.

Rep. Tim Walz, D-Minnesota, lamented that this year’s report from the Institute of Medicine will be the last to examine the effects of Agent Orange. While the VA secretary can still add conditions to the agency’s list of presumptive diseases, the congressional mandate for new reports has expired.

Walz said he believes the VA will evaluate the medical evidence linking Agent Orange to new conditions honestly, but he worries the costs associated with providing benefits to veterans, especially those with hypertension, may influence the agency’s decisions.

“I don’t see how they could not look into the economic impact of it,” he said.

“Congress capitulated its responsibility to be a partner in this,” Walz added. “The long-term impact of wars stretches for decades obviously. The backlog at the VA was not caused by the current group of warriors. It’s 40 years after the war ends that people start using the VA.”

Karl Pritchard served 22 years in the Navy before retiring to Norfolk, Virginia. His service included a tour in Vietnam flying aircraft interception missions from an airfield outside of Saigon, the former South Vietnam capital, in 1962. That was three years before the U.S. officially entered the war, but the military had already begun spraying Agent Orange and other defoliants.

Pritchard was diagnosed with an aggressive form of bladder cancer two years ago and had to have his bladder removed.

“I assume I was exposed. I don’t know. They don’t tell us these kinds of things,” Pritchard said recently before an oncology appointment. He receives experimental treatments every three weeks to prevent lingering cancer cells from spreading to other parts of his body.

“It changes you, losing your bladder,” he said, describing the external urine pouch he wears. “It gives you a new normal. Every hour or so, you gotta make sure you empty that thing, otherwise you make a tremendous mess.”

It’s not how the 78-year-old imagined living out his final years, he said. He started to file a claim with the VA a couple of years ago but stopped when an official told him he wasn’t eligible for compensation. He hasn’t bothered to revisit the process.

“I might apply,” he said, “if someone tells me it’s not a waste of time.”