"I remember just looking in the mirror and thinking, 'I have cancer?'" Daniela said.
Eight months ago, she was diagnosed with a childhood kidney cancer called Wilms Tumor.
"I wasn't going to have pity for myself," Leon said. "There was no room for that. Whatever I had to do to cure this needed to get done."
Chemotherapy and other drugs had a dramatic effect.
"Her tumors got smaller," said Dr. John Goldberg, Assistant Professor of Clinical Pediatrics at the University of Miami Miller School of Medicine in Miami, Fla. "The tumors in her lungs went away. They evaporated. Then, low and behold, we do an echocardiogram, and her heart function has gotten worse."
It's a common chemo side effect. Studies show 20 years after treatment, childhood cancer patients' risk of death from heart problems is more than eight times greater than those not treated for cancer.
"Children that are 30 year survivors have about a 15 times greater chance of getting congestive heart failure," said Dr. Steven Lipshultz, Chairman of the Department of Pediatrics at the University of Miami Miller School of Medicine.
To reduce that risk, doctors developed a new regimen -- adding a drug called DZR to the standard chemo. Five years later, kids treated with DZR showed much less heart damage but still benefited from the chemo.
Now, Leon gets treatment that fights cancer and protects her heart.
"In short, it allows us to continue giving her the chemo that she needs to survive," Dr. Goldberg said.
So she can keep fighting for a healthier future.
Childhood cancer survivors also have a 60 percent higher risk of developing more cancer, brain tumors or depression as adults.