The former footballer, and Ex On The Beach star, promised to ensure that Azaylia’s name “lived on” and that her legacy was “remembered”.
Azaylia Diamond Cain was diagnosed when she was eight weeks old and a fundraiser to try to help save her life had reached more than £1.5 million.
Sharing a photo of himself holding his daughter’s hand, Cain wrote his daughter had filled his soul with pride.
“My heart is shattered”, he wrote on Instagram.
“You gave my life purpose, my face a smile, filled my heart with love and my soul with pride.
“I can’t put into words my sadness and pain, there aren’t words to describe it. I love you with every ounce of my body and I miss you so much already.
“You made me a better man. You made me the person I’ve always wanted to be. You’ve taught me more in your 8 months than I’ve learned my whole life. I don’t know why you’ve been taken away from me and my heart aches in your absence.
“But I promise you that your name with live on. I will carry your name across every ocean, along every road, to the top of every mountain and across the whole globe.
“Your name will live, your legacy will be remembered and I will seek peace in living as your vessel to continue inspiring, giving strength, spreading joy and saving lives in your name, with your spirit, as your father until we meet again.”
Cain said she had “saved” his life and given him a “second chance”.
“I am blessed, I am honoured and I am privileged to be your father,” he wrote.
“I would go through all of the pain again and again. Because what you gave me in those eight months will live with me for eternity.”
Cain ended his post by sharing lyrics from the song “I Wanna Be like You” from Disney’s The Jungle Book.
The reality TV personality and Azaylia’s mother Safiyya Vorajee had been raising money for her to get specialist cancer treatment in Singapore.
After a successful bone marrow transplant, her leukaemia had rapidly multiplied and she had gone into a full relapse.
Doctors said chemotherapy would not be enough to cure her.
In November, the couple made a plea for people to register as a stem cell donor after being told their daughter required a transplant, which led to 41,000 people applying within 48 hours.