A High Court judge is to decide whether a seven-year-old boy can undergo radiotherapy treatment following surgery on a brain tumour.
On Friday, Mr Justice Bodey heard that Neon Roberts' mother Sally did not want doctors to begin radiotherapy treatment.
Ms Roberts, 37, of Brighton, East Sussex, told a High Court hearing in London she feared that radiotherapy would cause Neon long-term harm.
But doctors said Neon might die within months without radiotherapy treatment and urged the judge to give them the go-ahead.
Mr Justice Bodey said he would announce his decision later.
He said neither any hospital where Neon received treatment nor any medic involved should be identified in reports.
Neon's father Ben, who lives in London and is separated from Ms Roberts, had agreed to radiotherapy but was "apprehensive", the court heard.
Mr Justice Bodey said Neon's illness was the "stuff of every parent's nightmare".
He said he would balance what radiotherapy treatment would achieve against the "downsides".