I've got no experience with cancer in cats, but have you considered seeing a specialist? I'd be uncomfortable treating for cancer when there really hasn't been a diagnosis.
I hope you get some answers soon, ydono. Best wishes for you and Dana!
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."