Recurrent adem, being treated by rheumatology now

Hey all, I realize this support group is made up of mostly adults that's have had ADEM, but I'm here on account of my son. He's nine, and he's had adem seven times since 2008 when he was three. Metrology is at a loss so they are enlisting the help of pediatric rheumatologist, which are wanting to put him on meds that MIGHT control symptoms...we won't know unless he never gets sick again, which lets be real, it's just a matter of time until he does. The thing is, these meds can cause cancer. I've not had a real in depth conversation about it with the doc but I feel like I don't want Dylan on these meds that can cause cancer which can take his life for a chance that he never get adem again. Would it even be worth it? The first med they tried him on was Imuran which caused vomiting so they discontinued that. Now he's just on 25 mg oral prednisone. I have read countless articles about cannabidiol and success with ms patients that have demyelination, which is present with adem as well. I've consider moving to a state with medical marijuana just to trial it. No side effects so I feel like it couldn't hurt. Any thoughts or questions for me?