In a feat of strength and courage, a group of cyclists is embarking on a three-day, 576-kilometre ride from Toronto to Montreal.

They’re doing it to raise money for pediatric cancer research as part of the CIBC 401 Bike Challenge. But their grit pales in comparison to the bravery of the children they are riding for.

One of those children, 12-year-old Kathryn Stewart, has endured more than any child should ever have to. For more than half her life, Kathryn has battled neuroblastoma.

Her family has been through three bouts of a disease that has nearly claimed Kathryn’s life.

“To date, I have had 32 rounds of chemotherapy, 22 rounds of radiation, 17 surgeries, 2 bone marrow transplants and six months of immunotherapy here at Sick Kids,” Kathryn told the crowd that gathered outside Sick Kids Hospital for the cyclists’ send-off.

The brave girl told CTV Toronto that she loses hope sometimes, “but my family has always been there for me.”

Kathryn’s mother Heather says it’s been “gut-wrenching” to watch her daughter deal with the illness.

“As a parent, you’re always the one to fix things, and we can’t fix this,” Heather Stewart told CTV Toronto.

Neuroblastoma is a cancer that forms in developing nerve cells. It is the third most common childhood cancer, and only 50 per cent of those diagnosed will survive.

As the cyclists riding for pediatric cancer heard Wednesday, neuroblastoma is particularly difficult to treat because it has a tendency to recur.

Oncologist Dr. Meredith Irwin calls the disease “very devastating.” But she offers hope.

“For that disease in particular, we’ve had a lot of new types of treatment – a lot of which has been found based on fundraising money and research,” Irwin told CTV Toronto.

As the cyclists set off Wednesday on a gruelling ride to Montreal, they continually remind themselves of who – and what – they are fighting for.

“As hard as it’s going to be for me out there, they’re fighting this fight every single day,” said participant Lesley Taylor.

It’s a fight Kathryn Stewart hopes she’s finally won.

“I just pray that it’ll never come back,” she said.

With a report by CTV Toronto’s Janice Golding