Just last spring, six-year-old leukemia victim Emma Whitehead was "near death," having gone through chemotherapy twice without success.
But then her parents put Emma through an experimental treatment at Childrens Hospital of Philadelphia.
They infected her with a version of HIV, reprogrammed to attack cancer cells.
Whitehead almost died, but the treatment worked and now she's in remission and doing cartwheels all over her house.
Grady says the treatment hasn't worked for all patients.
It worked completely on three adults. Four treated adults have merely improved. A child relapsed. The treatment failed two adults completely.
Here's the thing though: Each of these patients was a "hopeless" case before trying the treatment. So any success is huge.