My uncle had bowel cancer and promptly went to California for operation and treatment. So far so good. He did not trust the NHS and was lucky enough to have medical insurance and enough dosh for the flights etc.
One thing that is recommended is a complete change of lifestyle to reduce stress. Whatever your wife REALLY wants to do with her life, get on and DO IT. It won't do any harm and it might just be enough to tip the balance in her favour.
Good luck to you all.