When Amy Jones’ dad, Paul, was diagnosed with glioblastoma last month, she wondered whether it might be tied to his time in Vietnam.

Then, last week, when Sen. John McCain, R-Ariz., also a Vietnam veteran, was diagnosed with the same aggressive brain cancer, Jones searched online for glioblastoma and Vietnam vets.

She soon learned the disease is one of a growing list of ailments that some Vietnam veterans and their relatives believe is caused by exposure to Agent Orange, the toxic herbicide sprayed during the war.

“Honestly, it’s not easy to even admit that this is happening, let alone to even talk about it,” said Jones, whose 68-year-old father has had surgery to remove a brain tumor and now is receiving radiation treatments. “It’s only been six weeks. It’s such a devastating diagnosis.”

McCain’s diagnosis comes as the U.S. Department of Veterans Affairs is under increased pressure to broaden who’s eligible for Agent Orange-related compensation. During the war, the military sprayed millions of gallons of the herbicide in Vietnam to kill enemy-covering jungle brush, and in the process, may have exposed as many as 2.6 million U.S. service members — including McCain.

News of his illness has prompted Amy Jones and others to call on the VA to study a possible connection between their loved ones’ Agent Orange exposure and glioblastoma.

Under current policy, the agency makes disability payments to veterans who develop one of 14 health conditions, but only if they can prove they served on the ground in Vietnam, where the chemicals were sprayed. Veterans who served off the coast in the Navy and those with other diseases not on the list — such as brain cancer — are left to fight the agency for compensation on a case-by-case basis.

Those with glioblastoma — or widows seeking survivor benefits — must prove the disease was “at least as likely as not” caused by Agent Orange, a cumbersome process that often takes years and more times than not results in denial.

Although McCain primarily served at sea from the deck of an aircraft carrier — and survived more than five years in a prison camp after his plane was shot down over North Vietnam — the VA would presume he was exposed to Agent Orange because he also spent time on the ground in Saigon.

Still, McCain never has sought to connect any of his health troubles, including prior bouts with skin cancer, with Agent Orange exposure and has a mixed record when it comes to compensating fellow veterans for wartime exposures. His office did not respond to emailed questions about a possible link between glioblastoma and the chemical.

As a senator, McCain voted to approve the original 1991 law that directed the VA to presume every veteran who served in Vietnam was exposed and to begin compensating those with illnesses scientifically linked to it.

In 2011, however, as many Vietnam veterans aged into their 60s and 70s and annual disability payments to them swelled to more than $17 billion, McCain spoke in favor of an amendment that would have required a higher standard of scientific proof before any new illnesses would be covered.

The goal, McCain said in a floor speech, was to ensure that veterans who actually deserved compensation received it, “but at the same time not have a situation where it is an open-ended expenditure of taxpayers’ dollars.” The amendment was defeated — and since then, Vietnam vet disability payments have grown to $24 billion a year — and the episode damaged McCain’s reputation with veterans groups.

In a statement, a VA spokesman said the agency currently does not recognize a connection between Agent Orange exposure and brain cancer but is examining the topic anew in light of the questions that have been raised. In March, the VA asked a National Academy of Medicine panel studying the effects of Agent Orange to focus special attention on glioblastoma. (Previous reports by the group have not found a connection.) The VA also is asking about brain cancer in a sweeping survey of Vietnam veterans now underway.

VA data provided to ProPublica last fall shows that more than 500 Vietnam-era veterans have been diagnosed with glioblastoma at VA health facilities since 2000. That doesn’t include the unknown number diagnosed at private facilities.

ProPublica and The Virginian-Pilot reported last year how widows of Vietnam vets were banding together to push the VA to add glioblastoma to its list of diseases linked to Agent Orange. Through a Facebook group, they support one another and offer advice on navigating the VA’s labyrinthian process for seeking disability and survivor benefits.

Since news of McCain’s illness broke last week, dozens like Jones have joined the group, whose members mostly include widows and surviving relatives, but also some veterans living with the disease. “Every one of us, our phones were blowing up the day it came out” that McCain had glioblastoma, said Kathy Carroll-Josenhans, one of the group’s leaders.

The group now has some 450 members, about double its size in December.

One of their challenges is that the VA’s handling of claims related to glioblastoma has been somewhat inconsistent. Between 2009 and last fall, the Board of Veterans’ Appeals, the VA’s in-house tribunal for adjudicating benefit denials, issued more than 100 decisions in cases in which widows have appealed benefits denials related to their husbands’ brain cancer, according to a ProPublica analysis of board decisions. About two dozen won. (Here are two additional approvals from this year.)

Brad Riddell, a 35-year-old communications specialist living in Austin, Texas, is not a member of the Facebook group but immediately thought of his father when he heard about McCain’s illness. His dad, Jerry Riddell, served in a Navy construction battalion in Da Nang during the war and routinely came in contact with Agent Orange, which was used to clear brush before paving roads and runways.

Riddell was in high school when his father had a seizure while driving from work one day. A brain scan later that day revealed a tumor the size of a grapefruit and a medical term that still makes Riddell shudder: glioblastoma.

His father endured three surgeries — including two at MD Anderson Cancer Center in Houston — before doctors told him there was nothing more they could do. He entered hospice and died in February 1999, just 14 months after the diagnosis.

“I absolutely thought about dad when I heard about McCain,” Riddell said. “Anytime I hear that diagnosis, it just feels like, ‘Man, that person is a goner.’ It’s terrible.”

After his father’s death, Riddell’s mother gave him a bag of his military records and told him to hold onto them: “She said, ‘You need to have all these records in case there‘s ever a connection made between your dad’s cancer and Agent Orange.’”

In the wake of the McCain news, Riddell wonders if it’s time to pull the records out.

Heidi Spencer had a similar revelation a year ago. Her father, Jack Niedermeyer, died of glioblastoma at age 58 in June 2004. Her mother didn’t think to apply for benefits until last year when someone at the local Veterans of Foreign Wars post where she works suggested it. Spencer helped her mom fill out the application and the VA approved it in March.

“He never knew his cancer came from Agent Orange. He never talked about his service,” she said of her dad, who worked in a steel mill in Pittsburgh and had six kids.

Spencer, 42, found her dad’s commanding officer in the Marine Corps, who wrote a letter saying her dad had been sprayed by Agent Orange.

“The more you research it, the more it comes into light,” she said. “The VA needs to look at this, they need to link it and they need to look at his [McCain’s] diagnosis and whether or not the Vietnam War played a role in him getting his disease.”

In approving her mom’s claim, the VA wrote that glioblastoma was not recognized as a disease that automatically warranted benefits linked to Agent Orange but that “current medical research has shown a causal relationship between herbicide exposure and glioblastoma multiforme.” This is contrary to the VA’s official policy.

Regardless of McCain’s position on the matter, advocates hope his diagnosis will spark a conversation.

In a statement last week, John Rowan, the president of Vietnam Veterans of America, said he was saddened to learn “yet another Vietnam veteran” had been diagnosed with glioblastoma.

“Unfortunately, brain cancer is not on the presumptive list for exposure to Agent Orange,” Rowan said in a statement, “despite the efforts of our fellow veterans and their family members.”