A woman who does not want her seven-year-old son to have radiotherapy treatment following surgery on a brain tumor renewed her fight in the High Court of Justice in London on Thursday (December 20).
Sally Roberts, 37, fears radiotherapy will cause her son, Neon, long-term harm.
Doctors say Neon might die within months without radiotherapy.
On Thursday a High Court judge began hearing more evidence about the advantages and disadvantages of radiotherapy.
Earlier this week, a High Court judge ruled that Neon could have a second operation to remove cancer from his brain against Roberts' wishes.
Roberts wanted the second operation to be delayed until more doctors had been consulted.
But specialists said follow-up surgery needed to be carried out urgently.
Cancer expert Professor Karol Sikora:
"Doctors don't recommend these things for fun. They are doing it for a reason. Obviously we are not party to those reasons, but, you know, this is the normal way in which cancer is treated- surgery followed by radiotherapy and in some cases chemotherapy."
A specialist treating Neon has described Roberts' comments as "sensible" and accepted that there could be side-effects to radiotherapy.
But he said without radiotherapy the little boy could die within a few months.
Roberts asked for the hearing to be adjourned until January to give her more time to investigate alternatives to radiotherapy.
But the judge refused her application and said a decision on radiotherapy had to be made.