Harding went public with her diagnosis on Wednesday in an emotional Instagram post, following a long absence from the platform.
“I understand this might be shocking to read on social media and that really isn’t my intention,” she wrote. “But last week it was mentioned online that I had been seen in hospital, so I feel now is the time to let people know what’s going on and this is the best way I can think of to do so.”
Harding said she was diagnosed earlier this year and, weeks ago, learned it had “advanced” and spread to other parts of her body.
She says she is currently undergoing weekly chemotherapy treatments and “fighting as hard as I possibly can.”
She thanked her support system and health care providers, calling them “heroes.”
“I am doing my very best to keep positive and will keep you updated here with how I’m getting on,” she said. “In the meantime I hope you’ll all understand and respect my request for privacy during this difficult time.”
Harding was a member of the English pop group Girls Aloud, which was active for much of the early 2000s.
Their last album, “Out of Control,” was released in 2008. They also released an anniversary single in 2012.
The band also included Cheryl Cole, Nadine Coyle, Nicola Roberts and Kimberley Walsh, who have offered words of support since Harding revealed her health struggle.
“You have always been able to achieve miracles when needed!!” Coyle wrote in a comment to Harding’s post. “I am here for the all the way & always will be!!!”