The footage was then played back to their parents, who witnessed how their children really felt and what their parents meant to them during their treatment.
The film, created by Cancer Research UK Kids & Teens, highlights how a diagnosis affects the children, as well as those around them.
“My mum did cry sometimes, but it was strange to see my dad cry, because I’d never seen him like that before,” said 12-year-old Bella, who was diagnosed with acute lymphoblastic leukaemia in 2012, while on holiday with her family.
“When my hair started falling out, he was devastated. In the end we just had to shave most of it off.”
Bella’s dad Andy commented on how she still amazes him three years after completing her treatment.
“To see what my daughter has been through, I’ll never take her for granted,” he said. “That first 72 hours of Bella being diagnosed was really, really terrifying.”
Another child in the video is Nengi, 10, who received the news she had non-Hodgkin lymphoma when she was two years old.
“Sometimes my mum would be upset and I wouldn’t really understand why,” she said. “Seeing me like that, it broke her heart.”
After watching Nengi open up, her mum Janet, said: “I didn’t think I was strong until my daughter was diagnosed with cancer. I had to stop everything to be there for her. I’m surprised she remembers so much.
“She just wanted to be like every other child and now she is - she’s got an amazing heart.”
The film also features 10-year-old Rhys, who was diagnosed with a brain tumour when he was four. As part of his treatment, he took part in a clinical trial funded by Cancer Research UK. It also features eight-year-old Izzy, who was told she had leukaemia in September 2011.
Dr Áine McCarthy, senior science information officer at Cancer Research UK, said: “Each year, around 4,200 young people under 25 years old are diagnosed with cancer in the UK, and the strength that they and their families show under very difficult circumstances is inspirational.
“The good news is that today, more children like Bella, Nengi, Rhys and Izzy, are surviving cancer than ever before, and Cancer Research UK’s work has been at the heart of this progress.”
This Childhood Cancer Awareness Month, Cancer Research UK Kids & Teens is asking the public to make a donation or purchase a gold ribbon pin badge to support its work to find new, better and kinder treatments for children and young people with cancer. To find out more, visit: www.cruk.org/kidsandteens.