Zac Oliver, 4, of Broseley, Shropshire, was diagnosed with a rare form of blood cancer called Haploid. He is considered the only child in the UK with this particular strain.
The family and supporters helped raise money in just two months, which allowed him to go to Philadelphia for treatment.
Over 100 trucks took part in a convoy at Shropshire to collect money for him.
He and his family have now landed in America.
A four-year-old patient underwent chemotherapy and received treatment at the Children's Hospital at Telford Princess Royal and Birmingham Children & # 39; s Hospitals.
On the flight to the States, mother Zac, Hannah, cried out, saying:
"It's tears of joy that we did it, we're on the plane, I just want to thank everyone, wish us luck."
Zac will receive a new treatment at the Children's Hospital in Philadelphia.