The actress and writer, who also created Mrs Merton, has previously been treated for bladder and eye cancer.
She is taking part in an appeal in her home city of Manchester that is asking patients and carers to help improve standards of care and said: "I've had cancer and my brother's had cancer and we know how it affects people."
Nicola Cook, of Macmillan Cancer Support, said: "Caroline's one of Manchester's own — she's loved here and people identify with her. We hope that if people see that Caroline is sitting down and talking to us, then maybe they'll know they can too."
She recently took part as one of the cast of an animated children's series for the BBC.
She is also the voice of hit Channel 4 show Gogglebox and said she would continue working on the show.