Kathryn Cartwright has undergone several transplants.
A lung condition means she cannot walk far.
She is one of 200 people who attended the Hardest Hit rally in Birmingham, part of several rallies across the county where disabled people and carers protested against benefit changes.
Ms Cartwright, from Birmingham, says she has had her employment support allowance stopped, even though she is unable to work. She is appealing against the decision.
The 20-year-old developed leukaemia when she was 16 and has undergone two bone marrow transplants and a liver transplant.
On a good day, she says, she can walk upstairs.
She said: “We don’t want to be on benefits, we would love to work but it is not possible.”
Maria Miller, the minister for disabled people, said the government wanted to put the integrity back into the benefits system to make sure the £40bn is going to be spent in support of disabled people.
Jack Dromey, Labour MP for Birmingham Erdington, who attended the rally, said: “Reform the benefits system – without hesitation.
“Penalise the disabled – never.
“That’s why all of the organisations representing the disabled are saying with one voice this is wrong.”