I took Methotrexate for 15 years for an autoimmune illness called Sarcoidosis. I know it was a very potent drug as I had to have regular monitoring. I seemed to remember they told me it was also used for leukemia sufferers.
I don`t know anything about the drug but chemo knocks out the immune system so I suppose that is why it is prescribed for arthritis. My cousin`s husband developed lupus and he had it really bad. It settled in his heart (and he was only about 40 years of age) The powers that be in a London hospital prescribed him chemo as a last resort to see if they could stop his immune system attacking his own body (it didn`t work).
I've had methotrexate for rheumatoid arthritis, remember one of the nurses saying it's a tiny amount compared to that used in chemotherapy but when you look in to how it works it makes a lot of sense. I'm on and off it though between infections and raised liver enzymes.
I know a couple of people who are on oral chemotherapy.