The Challenge star Ashley Cain, 30, has recently opened up about his infant daughter’s health three months after he first revealed she had been diagnosed with leukemia.

On Monday, he wrote on Instagram that his 5-month-old daughter, Azaylia Diamond, has started a stem cell transplantation procedure.

Cain wrote, “Today was by far the biggest day of our lives. One that we have been hoping, wishing and praying for. The day Azaylia received her stem cell transplant and begins the toughest journey imaginable to save her precious life!”

“We believe in you princess,” he continued. “You are strong, you are mighty, you are courageous and God is with you! You got this Likkle Lion. We love you! LETS GO CHAMP!”

Cain’s update comes a day after he shared on social media that his daughter “had relapsed and her leukemia had returned,” according to PEOPLE.

He said that the family had found a stem cell donor after doctors determined that she needed a transplant.

He said, “It’s hard to put into words how grateful we’re are for everyone that’s supported, shared and registered to be a donor to help save Azaylia’s life. Thank you to EVERYONE! It’s truly overwhelming!”

“However, after Azaylia’s second round of chemotherapy, we were informed that Azaylia had relapsed and her leukemia had returned,” Cain continued. “Which highlights how aggressive her cancer is and shows how crucial this transplant will be. It also means she will have to go into transplant with Leukaemia, which is far from what we wanted.”

He explained that the family “were also told that because of her age and the aggressiveness of her cancer, she is in the high risk category for transplant complications and the poor risk category for transplant success.”

“Hearing that news was absolutely devastating and has made everyday 10x harder for us and hurt even more than it already did!” he added. “We go into transplant tomorrow for 4 to 9 months and have been told that it’s going to be incredibly tough, that she is going to be very very poorly and it’s going to get a lot worse before it gets better!”

However, he noted that the family is “doing our best to remain strong and positive for our daughter.”

Cain wrote, “She made it past the first stage of treatment against the odds and we truly believe that she will do the same this time around!. She is a fighter, she will do this and we will be by her side every step of the way!”

Last week, Cain said his daughter had entered her “3rd and toughest round of chemotherapy yet. Please keep Azaylia in your prayers. LETS GO CHAMP.” The article was published on PEOPLE.