Toby Nye, now five, was diagnosed with the rare neuroblastoma cancer on his fourth birthday.
His family - backed by Leeds United - launched a campaign that managed to raise the Â£200,000 needed to pay for antibody treatment, which was not available on the NHS.
And after completing the treatment this month, the youngster is now cancer-free, according to his official Twitter page.
"Our amazing little superhero has smashed it," the post said.
"His end of treatment tests show no evidence of disease, he is in remission.
"He still has a long way to go as he needs to stay cancer free for five years. We would like to thank everyone for your support We as a family will always appreciate it."
It comes just weeks after it was revealed that the treatment used on Toby, from Osmondthorpe, will now be available on the NHS.
The drug, called dinutuximab beta, was recommended by the National Institute for Health and Care Excellence (NICE) under final draft guidance published on July 12.