Oscar Saxelby-Lee, from Worcester, had stem-cell treatment in the UK, but tests showed cancer was still present.
He flew to Asia with his parents for CAR-T therapy, with the help of £500,000 raised to pay for it through crowdfunding.
His mother, Olivia Saxelby, said they would know in a week if it had worked.
Mrs Saxelby said the therapy, which is not available on the NHS, is specifically developed for individual patients and involves reprogramming their immune system cells, which are then used to target the cancer.
She said it had been an “emotional ride” since her son received the treatment on Christmas Eve.
“It feels surreal, but it also feels like nothing has changed because we just haven’t seen a difference yet and we don’t know what’s happening. It’s really tough,” she said.
“It’s gone in. It was as quick as five minutes and now it’s waiting.
“It’s done and there’s no going back. It was such a big step to take.”