Alexis has since had a bone-marrow transplant and been in and out of Starship Children's Hospital undergoing chemotherapy treatment. She is now in remission.
Choking up, Mr Page said seeing his little girl suffer had been difficult.
"She's a miracle kid. I just looked at her and thought, 'What can I do for her and for everyone else with cancer?' I heard about this and knew I had to do it to help raise funds for cancer research and for all the families who have gone through what we went through."
Mr Page, who raised just over $3500 for his efforts, said it was a "no brainer" to complete the ride on a unicycle, as he had been riding them since he was a boy.
He took part in the Unicycle World Championship competition in Italy last year.
Alexis' father, Luke Thrush, said his father-in-law had been a great source of support and motivation for him and his partner, Kristin Page.
"I'm very proud of him. He's been a great support to us, with everything that's happened with Alexis, and he's a great grandfather."
Yesterday's event pulled in $2.1 million for Cancer Society Auckland.
Chief executive John Loof - who was also out on his bike on the weekend - said the money would go towards medical research programmes and clinical trials.