Jillian Vardy holds her son, Trevor, at Children's National Medical Center. At 5 months old, Trevor was diagnosed with a brain tumor. (John Kelly/The Washington Post)

When people ask Lindsay Kilburn what she does, her response can stop the conversation cold. She’s a pediatric oncologist at Children’s National Medical Center, specializing in cancers of the brain. Mustn’t that be indescribably sad?

No. “I wish more people could come into our clinic and see how amazing these kids and their families are, their energy and spirit,” Lindsay said.

You certainly can’t argue with the spirit of the almost-2-year-old Trevor Vardy, whom I watched pinball through the atrium at Children’s Hospital after an appointment not long ago.

“He’s not always this wild,” said his mother, Jillian Vardy of Crofton. But after what Trevor’s been through, no one would begrudge him a bit of exuberance.

In July 2011, Trevor, then 5 months, was at the beach with his family. He started vomiting, not an uncommon thing for a kid. It looked like a stomach bug, said the first doctor they saw. When it didn’t stop, Trevor was checked into a hospital overnight for some fluids. He didn’t improve and a CT scan revealed a tennis-ball-sized tumor on the occipital lobe of his brain. Two days after he’d first gotten sick on the beach, Trevor was in a helicopter on his way to Children’s Hospital.

Suresh Magge, a pediatric neurosurgeon, operated, carefully teasing the tumor — a type known as an ependymoma — away from healthy brain tissue.

Trevor was in the pediatric intensive-care unit for a week, then moved to the neurology ward. Jillian, a nurse, and her husband, John, who sells heating and air-conditioning equipment, waited to see what sort of boy would emerge

“That was the thing I was worried about,” Jillian said. “I was afraid when he woke up, as things started to come back, he would be a different kid. It took a couple of weeks — and there were some pain issues — but once he came back around, he was back to himself.”

Even when a tumor is fully removed, cancerous cells can take root elsewhere. And so Trevor started six months of chemotherapy under the direction of Lindsay.

Cancer cells grow quickly, so chemotherapy drugs are designed to attack fast-growing cells. Human hair is composed of fast-growing cells, too, which is why hair loss is a common side effect of chemotherapy. Trevor lost his, but he soldiered on.

“In some ways, I think it was good he was so little, because he couldn’t tell me how bad he really felt,” Jillian said. “So it was nice to, in my mind, pretend that it wasn’t that bad.”

Infections meant Trevor was back in the hospital for Halloween and then for Thanksgiving. Whenever he was at Children’s Hospital, his older brother, Jaxon, would visit.

“I think that’s really what kept him going,” Jillian said. “He just wanted — and still wants — to keep up with his brother.”

Every parent has imagined the worst, let their thoughts take them on a horrible trip when they feel a feverish forehead, see a bump or a bruise. How did Trevor’s mom and dad ever cope?

“All I ever said was, if he could live, I didn’t care what else happened,” Jillian said. “And I still think that.”

Still, it was the toughest year she ever hopes to experience.

“It was horrible,” she said. “There’s still a time every day, even for just a second, where I think to myself, if it ever came back . . .

She stopped.

“But I look at him and I’m like: You know, he’s telling me that he’s fine. I decided to listen to that.”

Lindsay said that while the overall cure rate for pediatric cancers is 70 to 80 percent, brain tumors are tougher, with a cure rate of 50 to 60 percent. Hopefully, research will result in new therapies that will allow more kids to have outcomes like Trevor’s, who, according to his last MRI, is cancer-free.

Said Lindsay: “He keeps me going when I get to see him, for all the other kids who are in treatment.”

Helping Children’s

The last thing the parents of a sick kid should have to worry about is whether they can afford the treatment that will save their son or daughter’s life. Thankfully, around here, they don’t have to. No children are turned away from Children’s Hospital because their parents don’t have insurance.

The readers of The Washington Post help make that possible by donating to our annual fundraising campaign. Won’t you give? You can make a tax-deductible donation by going to childrensnational.org/washingtonpost or sending a check (payable to Children’s Hospital) to Washington Post Campaign, P.O. Box 17390, Baltimore, Md. 21297-1390.

To read previous columns, go to washingtonpost.com/johnkelly.