BethAnn Telford continues her marathon career despite suffering from brain cancer. She will run in this Suday's Marine Corps marathon. (John McDonnell/THE WASHINGTON POST)

Just 10 days after she completed the Ironman Triathlon in Kona, Hawaii, BethAnn Telford was back at work at the U.S. Government Printing Office in Washington, where each time she emerged from her office, she earned a new admirer. Colleagues, security guards, guests in the building — all peppered the 43-year-old special events coordinator with congratulations for finishing one of the world’s toughest races. Many just stared at her in amazement.

“Damn, that’s farther than a drive to Richmond,” said one woman, marveling at the 140.6 miles Telford covered in the swim-bike-run competition. “I can’t even imagine.”

Telford’s joy in the accomplishment was tempered by the pain behind her left eye. The brain tumor she has lived with for eight years hurt more than usual. It had been acting up since she finished the Ironman race Oct. 13, and the cabin pressure on the flight home from Hawaii hadn’t helped. Sometimes the tumor caused wave after wave of fatigue, slurring and memory loss.

But none of that will be enough to stop her from competing in Sunday’s 37th Marine Corps Marathon. It will be an emotional day for many of the race’s participants, some of them U.S. military veterans wounded overseas. It will be Telford’s 11th consecutive Marine Corps Marathon, a race that took on new meaning in 2004.

That year, as she cleared Hains Point, between mile marker 18 and 19 on the course, she felt a pop in her head. Something detonated, and Telford’s vision went blurry. When she looked up at the sky to clear her head, the only image that sticks in her mind was a light post that was set alongside the path.

The 37th Marine Corps Marathon begins at 7:55 a.m. Sunday. Rolling road closures will be in effect along the course from 4 a.m. to 5:30 p.m.

“I wiggled my head around, almost like it was a severe headache, where you start seeing stars. I saw that light post,” she said.

She finished the race, but barely. In the days that followed, she began to run into furniture in her Fairfax home because she forgot where it was. Then seizures set in. Doctors soon found a large tumor behind Telford’s left frontal lobe, an egg-shaped growth wrapped around a major blood vessel in the brain.

“She was in her 30s at the time. You don’t think something this catastrophic is going to happen . . . especially to somebody that is young and fit,” said Bob Latin, who has been Telford’s partner for 11 years. “I was stunned.”

Over the past eight years, Telford has endured two major brain surgeries at Johns Hopkins Hospital to remove the growth and regrowth, and she is scheduled for a third early next year. The cancer has spread to her bladder, bringing on several more surgeries, and now she fears that she has a tumor near her larynx, which she said was discovered a few weeks ago before she left for Hawaii.

Telford has learned how to walk again. She has learned how to see again, after losing the vision in her left eye. She has learned how to speak differently, because sometimes the cancer causes her to stutter and slur her words.

But she has run in at least one marathon every year since her 2005 diagnosis. Telford has completed the Boston Marathon in each of the past three years, and this month’s Ironman was her second in four years.

A chemotherapeutic drug called Temodal and Telford’s ferocious will have made it possible. She hired a local triathlete trainer, Alyssa Morrison, to design a diet and daily workout regimen, which includes daily runs through downtown Washington. The surgeries have allowed intermittent periods of strength over the past eight years, but Telford has nonetheless defied medical odds by continuing to train for and finish grueling races.

“This still is pretty rare,” said Derek Johnson, a neurologist at the Mayo Clinic in Minnesota, about Telford’s ability to run with brain cancer. “It is, though, happening more and more commonly than it did in the past. With improved treatments for disease, better surgical options, radiation options, just general improvements in quality of care, I think we see people living longer and living a fuller and more active life than what was possible previously.”

The Ironman course nearly broke Telford two weeks ago. She said she struggled with the open-ocean swim, and steadily vomited as she tried to hold down food on the 112-mile bike portion of the race. She eventually crossed the finish line in 15 hours, 13 minutes and 42 seconds, carrying a flag emblazoned with the names of cancer victims.

Turning around two weeks later for another marathon will be one of the most difficult tests of her life, she said. With uncertainty surrounding her condition and another brain surgery looming in the coming months, this may be the last race Telford runs.

But there is no way she would skip Sunday’s race, she said. The course has changed since 2004, but still makes a loop around Hains Point. Telford covers that stretch regularly, often pausing near the light post that is a reminder of how this all started.

“When I do my runs, and go past that area sometimes, the girls that I run with, we gesture at that light post. Not in a kind way sometimes,” Telford said. “The course has never changed from that area, from where my journey with brain cancer started. I’ll never forget that.”