Iva Tatounova said the six-year-old’s recovery was proof that proton-beam therapy should be “the first choice” of treatment for children with his condition.
Ashya’s parents, Brett and Naghmeh King, took their son back to the centre in the Czech capital, one year after they sparked a Europe-wide manhunt when they removed him from a UK hospital.
Ms Tatounova, director of the Proton Therapy Centre, told ITV’s Good Morning Britain: “He’s doing fantastically. I’m over the moon, actually.
"He walked to the centre on his own feet. He didn’t need a wheelchair. He’s speaking and playing with other kids and his siblings, and next week (he’s) going, for the first time, to a school.”
Proton-beam therapy is not widely available in the UK, but Tatounova said “it’s less aggressive”.
Police launched an international search for the King family after Ashya was removed from Southampton General Hospital, without doctors’ consent, in August last year.
A High Court judge later approved the move to take Ashya to Prague.