Methotrexate is used as a cancer drug as well but In larger doses than given for RA. May we have some more info with this question. Your dr will have to tell you about the dosage and how often you take it.

I was told by a Rheumatologist that some cancer drugs works well on inflammations so that's why they are used for RA.

some cancer drugs work for RA

Your rheumy should tell you that. I just looked it up and it's been used for breast cancer. Didn't see it as a drug for RA

How often is Cytoxan administered?