But seven years ago, his parents were concerned by an unusual number of bumps on his head, reports CBS News correspondent Dr. Jon LaPook.
"Cancer did not cross my mind at all," said Eileen Mullin, his mother.
After several trips to the doctor, the Mullins received the worst possible news.
"It was a very aggressive cancer and we needed to start treatment right away," said Chris Mullin, Brian's father.
It was neuroblastoma, a rare but deadly form of childhood cancer. Although barely a toddler, Brian received aggressive therapy: chemotherapy, surgery, radiation and stem cell transplantation.
But then his doctor offered an additional step: an experimental treatment called immunotherapy, in which antibodies that target the cancer are injected into the bloodstream and attach to the tumor cell. One tagged with antibody, the cancer can be more easily recognized and attacked by the body's own white blood cells.
"They tested it on me and it was a success, so I hope it works on all other kids," Brian said.
In results released Thursday, immunotherapy improved the outcomes of patients with advanced neuroblastoma. After two years, 46 percent receiving standard treatment alone were free of tumor recurrence versus 66 percent of those like Brian who also received the antibody.
"It's wonderful to go and talk to a parent, whose child has just diagnosed with an advanced neuroblastoma and say the odds of being cured has increased dramatically," said Dr. M. Fevzi Ozkaynak with the Maria Fareri Children's Hospital at the Westchester Medical Center in New York.
Brian likes his odds and he isn't looking back.
"I've been through it, it was the past, time to move on," he said.
This new treatment is still experimental, but it's a step forward in the strategy of manipulating a person's own immune system to fight cancer.