A six-year-old Perth boy who came to national prominence due to a legal battle over treatment for a rare brain tumour has died.

Oshin Kiszko underwent surgery in December 2015 after being diagnosed with cancer, and specialists recommended the boy receive follow-up chemotherapy and radiotherapy treatment.

But his parents, Angela Kiszko and Adrian Strachan, refused permission for the treatments, opting to pursue alternative therapies amid concerns about side effects from the radiation.

They argued the treatments would destroy Oshin's quality of life, and that palliative care was more appropriate.

They took Oshin's doctors to the Family Court, which earlier this year ruled the boy should undergo chemotherapy.

Oshin's parents remained firmly opposed to the treatment, and the case returned to court in May because the doctors again wanted him to have radiation treatment.

However, the case was adjourned after the parents gave an undertaking they would let their son continue to have chemotherapy.

The court heard evidence Oshin would have between a 30 and 50 per cent chance of survival for five years if he received both chemotherapy and radiotherapy.

In September the court ruled Oshin be allowed to only receive palliative care.

The Family Court said that "by August 2016, specialist medical opinion confirmed that the delay in therapy had substantially reduced Oshin's chances of a cure, which are now remote".

Justice Richard O'Brien said Oshin's relationship with this parents weighed heavily in his decision to allow palliative care.

"I am deeply concerned that any perpetuation of the conflict over Oshin's treatment will continue to diminish the ability of his parents to focus their energies solely on the provision of that support and love directly to him when he needs it most," he said in September.

Last week Ms Kiszko posted a tribute to her son on social media, revealing he was close to death.