A High Court judge is expected to decide on Friday whether a seven-year-old boy can have radiotherapy treatment, following surgery on a brain tumour, against his mother's wishes.
Sally Roberts, 37, a New Zealander who lives in Brighton, East Sussex, renewed her fight for alternative treatment for her son Neon at a High Court hearing in London.
Mr Justice Bodey indicated that he would make a ruling on Friday.
Ms Roberts says she fears that radiotherapy would reduce Neon's intelligence quotient (IQ), shorten his life, put him at risk of having strokes and make him infertile.
She said she thought that there was "credible" alternative treatment.
A specialist treating Neon has accepted that there could be side-effects to radiotherapy, but he said without radiotherapy the little boy could die within a few months.
And Victoria Butler-Cole, who is representing doctors involved in Neon's care, told the judge that Ms Roberts was proposing "experimental therapies", which are unproven, as alternatives to radiotherapy.
Neon's father Ben, who lives in London and is separated from Ms Roberts, has agreed to radiotherapy but is "apprehensive", the court has heard.
Earlier this week, Mr Justice Bodey ruled that Neon could have further surgery against Ms Roberts' wishes.
Ms Roberts wanted a second operation to be delayed until more doctors had been consulted but specialists said follow-up surgery needed to be carried out urgently. A doctor treating Neon told the judge that the operation - performed on Wednesday- went well.