"It's a bit strange to say, but it's true," his mother, Kaci Johnson, said.
Duncan was 3 years old when he was diagnosed with Burkitt's Lymphoma. He spent six months at the Children's Medical Center at the Medical College of Georgia.
He remembers the toy guns and foam disks he shot at doctors any time they approached with a needle.
"They had these air hockey tables, too. Duncan loved it," Kaci Johnson said. "It made an unbearable situation bearable."
The family is one of countless many to have benefited from the fundraising and awareness campaign of 12 Bands of Christmas.
The nonprofit returns this year with not only an annual concert and CD, but also a revamped mission to fight pediatric cancer.
"Last year, we read the news that 12 Bands could be dissolving. We knew we couldn't let the thing wither on the vine. Too many kids are fighting to turn away now," said Turner Simkins, a member of 12 Band's advisory board whose son, Brennan, is facing acute myeloid leukemia for the third time.
The Augusta boy, a second-grader at St. Mary on the Hill Catholic School, is being treated at St. Jude Children's Research Hospital in Memphis.
"There's this need for research," Simkins said, "and research takes money. With 12 Bands from Augusta, you draw an audience from Augusta. With a regional or national audience, we aren't always shaking down the same people."
While in and out of hospitals, Simkins said he meets people not just from Georgia or Florida or Alabama, but from throughout the United States.
"It hits you. There are kids like mine all across the United States," he said.
Since their son was diagnosed two years ago this January, the Simkinses have openly shared their story and seen the community rally in response.
"It's the stories that allow people to see what 12 Bands can really do," he said.
"It gives us a conduit in which to encourage people to be aware of pediatric cancer, not just our son's disease. Ultimately the goal is to find a cure."
Pediatric cancer research is often under-funded, according to the Rally Foundation, an Atlanta-based nonprofit dedicated to raising funds for pediatric cancer research.
Childhood cancer is the No. 1 disease that kills children, according to the National Cancer Institute of the U.S. Department of Health and Human Services. The NCI's spending on pediatric cancers research increased from $165.9 million in 2004 to $189.8 million in 2008, yet groups like the Rally Foundation say there's at least a $30 million gap between the money spent and the money needed.
Much of the research is also limited to adults, Kaci Johnson said.
"As a mother, you want to improve the quality of treatment for your kid. You want a treatment tailored to a child," she said.
"The less poison I put in my son's body, the better."
Still, Johnson said, she's thankful any treatment exists at all for her son, now a kindergartner at Episcopal Day School, where she teaches.
"We're grateful for the families who have gone before us," she said.
"Burkitt's Lymphoma is very rare, but treatable. Ten years ago, there was nothing they could have done, but the research is changing that. That's the reason he's here right now, laughing, being a kid, playing air hockey."