If I had a child with leukemia, I'd want them to go to St. Jude Children's Hospital in Memphis. I live fairly close, so I hear about all the discoveries and research they do. I think it's just the best place for a child with any kind of cancer, really. They surely do have the best life expectancies and outcomes.
Early detection is always important, but I think that's more vital in other kinds of cancers. With leukemia, you can't always tell, and people have been brought back from death's door when they receive treatment.
It's all about the quality of the treatment and how much the doctor knows about treating the disease.