4 April 2017 Last updated at 14:25 BST
Ollie Gardiner, from Aston Clinton, Buckinghamshire, was diagnosed in May 2015 and went through 10 cycles of chemotherapy and 34 sessions of radiotherapy before the cancer came back in September 2016.
Doctors said the tumour was "incurable", but the family decided to try and raise money to pay for a new type of treatment.
So far £425,000 has been raised, but the family still needs £15,000 to reach their target.
Ollie and his father, Peter Gardiner, spoke to BBC Three Counties Radio about the fundraising and pioneering treatment.
Peter said: "We're being treated in London on an outpatient basis, which is wonderful because Ollie can be with his friends and can go to school. Maintaining some normality is so important in cancer treatment.
"Friends, family, the wider community and people we don't even know are giving up masses of their free time just to help us, it's an incredible feeling.
"The support has been absolutely fantastic."
Speaking of the treatment he began in October last year, Ollie said: "It's been tough, but it's OK."
More than £400,000 has been raised for a 12-year-old boy who is undergoing pioneering treatment for a brain tumour.