I think that all immuno-suppressants will increase the chance of cancer as well as infectious diseases by the very nature of what they are. They decrease your immune system's response to those things. They also decrease your immune system's attack on your neuromuscular junction which is what you want.

I agree that I would be scared to totally give up the mestinon cold turkey. I would at least keep some on hand in case things get bad.

I imagine that your doctor hopes that the immuran will make it so that you don't need the mestinon.