When she ran her first marathon in 2005, the life of BethAnn Telford, special events coordinator for the Government Printing Office, changed dramatically.

She was running in the Washington, D.C.-based Marine Corps Marathon and coming around the corner at Hains Point. “That was like mile 19, 20, and I heard a — I had a huge pop in my head, and I thought maybe I was dehydrated,” she recalled last week.

But she wasn’t dehydrated. As time, tests and a slew of neurologists would soon discover, Telford, now 40, had a malignant brain tumor. More than five years later, as she prepares for her third brain surgery, three things drive her: training for today’s Boston Marathon, fundraising for the National Brain Tumor Society and working at the GPO.

A Harrisburg, Pa. native, Telford was working for Pennsylvania Gov. Tom Ridge (R) in 2001 when President George W. Bush named him secretary of Homeland Security. She moved to D.C. to work in his office and has since worked in the Office of the Chief Administrative Officer on Capitol Hill, too. She came to the GPO to work as an assistant to then-Public Printer Bruce James, and in her current role, she is responsible for events such as Take Your Child to Work Day and an annual outing for hundreds of GPO employees and their families to Nationals Park.

Telford, one of about 600,000 Americans living with a primary brain tumor, doesn’t betray her illness. She’s in better shape than most healthy Americans, and though her sight out of her left eye is limited and her memory often fails her, she rattles off a friend’s phone number without a problem. She has had two surgeries, the first five years ago this month. A pacemaker that regulates her bladder is delaying her surgeon’s ability to perform the next necessary surgery. Only about 30 percent of brain tumor patients survive five years after the diagnosis of a primary malignant brain tumor, according to NBTS.

The difficult odds don’t seem to faze Telford. Even in the marathon where her disease first reared its ugly head, she posted a personal record. When she missed qualifying for the Boston Marathon at last fall’s Marine Corps Marathon by just more than a minute, she turned around two weeks later and made the cut by less than a minute at the SunTrust Richmond Marathon — both times running on a stress fracture in her foot.

“Her pain tolerance is very, very high,” said John Carmichael, a UPS worker who lives in Loudoun County, Va., and runs with Telford.

Carmichael, 48, would know. He met Telford at a gym in 2007, and they trained for the 2008 Ironman Lake Placid. (Keep in mind that an Ironman triathlon involves a 2.4-mile swim, a 112-mile bike ride and a marathon, done without a break between events.) He remembered that Telford would get chemotherapy at Johns Hopkins University on Friday, then would run on Saturday and bike on Sunday.

“She didn’t want to sometimes eat or drink,” he said, “and I’m saying, ‘Hey, you gotta eat and drink. You’re doing all this training.'”

Carmichael will run with Telford again today at the Boston Marathon. They’ll check in with the race’s medical team before and after they run. He’ll carry Telford’s medical information with him, and as they run to the left of the course, he’ll be on her right to let her know when other runners are coming up behind her.

“If she needs to, she’ll grab hold for stability purposes, but I’m not doing anything for her,” he said. “She’s still taking every step.”

Though the Boston Marathon has been a longtime goal for Telford, it will not be her last race. The pair will run again in the George Washington Parkway Classic 10 Miler on April 25 and then as part of a team of almost 300 of Telford’s friends (including her black Labrador, Maverick) at the Race for Hope on May 2.

The Race for Hope raises money for NBTS and is a yearly highlight for Telford. She has already raised more than $30,000 as part of this year’s effort. The NBTS is so thankful for her efforts over the past five years that in 2009 it named a research chair for her, and it’s now being used to fund research “targeting radiation resistance in brain tumor stem cells” at Cleveland Clinic. It’s a small token of gratitude for so much work, said Kris Knight, NBTS director of community relations.

“It’s kind of ironic that her tireless efforts involve marathons and Ironmans that would make the rest of us exhausted,” she said.

Even as the tumor continues its march on her brain, Telford has not slowed down. She works a full schedule at the GPO, fundraises enthusiastically for NBTS and sets her sights high for the marathon of a lifetime. She said her times have improved since that fateful race in 2005.

“I think my first marathon was like five [hours], but then I went down to qualify and had to do a 3:50,” she said. “I’d like to do [the Boston Marathon] in four, but I’m not sure if that will happen. If I can do it in 4:30, 4:45, I’ll be happy.”