Cooper Barnes, 8, was diagnosed last May with glioblastoma multiforme, an inoperable, fast-growing brain tumour.

While his prognosis is not good, Cooper's parents, Justine and Russell, and his three siblings are determined to keep fighting.

He has had intensive treatment, including radiotherapy and chemotherapy, in the hopes of shrinking the tumour.

"We thought it was going well, but an MRI showed the tumour wasn't shrinking," Mrs Barnes said. He has been put on a fairly new drug that he takes fortnightly.

Cooper has had surgery to remove some of the tumour, but its complete removal is not possible as it's in an area that controls his motor skills.

"Through all this he has cried [only] once, and that was when someone put an IV in," Mrs Barnes said.

"He has taught us so much about courage and bravery and acceptance. He's said to his father that he wishes he didn't have this lump in his head ... we tell him that the lump isn't shrinking."

The family has tried to get Cooper into trial treatment programs in Germany, New York and Florida, but he is either too young or doesn't qualify.

"We have been told to prepare ourselves [for the worst], but how do you do that? We just need to get him through somehow."

Friends and Sunbury Heights Primary School mothers have rallied to help the Barneses, who have been forced to sell their home to pay medical bills and gave up work to spend time with Cooper.

Dubbed Mission Mums, the mothers' group has organised a fund-raiser.

Julie Chakey, one of the mums, and her son Tyler spend time with the family regularly.

Another Mission Mum, Cathy Williams, who has known the Barnes family since their children were in kinder, said:

"We have so many people to thank, we haven't even started collating everything. But we want to thank all of Sunbury and the Sunbury mums for all their help.

"And thank-you to the Mission Mums Julie Chakey, Ann-Marie Priestly, Michelle Wood, Helen Goldsworthy, Kylie Stephenson, Mandi Weir and Andrea LeBrenton-Hanson."

Mrs Barnes said the Mission Mums

had visited every business in Sunbury, asking for donations and selling wristbands.

The fund-raiser is on Thursday at the Sunbury Bowls Club from 6pm.

For inquiries or donations to Cooper's trust account, call Julie, 0425840579 or Cathy, 0425837458.