Cornwall toddler Jay Hensby is recovering from a tumour in his brain after undergoing treatment in the US, which cost £250,000.
Jay was diagnosed in February when doctors found a lump about the size of a golf ball.
After an operation in Bristol to remove the tumour, he was flown to Florida for "proton treatment" to remove any remaining cancerous cells.
The NHS funds specialised treatment for about 10,000 patients a year like Jay.
The cost of the treatments by the National Specialised Commissioning Group is about £480m.
Jay, two, from St Austell, has got another scan in six weeks, and could suffer some hearing or sight loss.
But his parents Julie and Dave are just glad to have their "little miracle" home.
Mrs Hensby said: "He might not have come through the op in Bristol, so it was the longest 27 hours in our lives."
Mr Hensby said: "It's been a rollercoaster ride for the last three months.
"At several stages we thought we were going to lose him.
"I'm just so glad he's back with us where he should be, with his family."