Welcome to Healthcare-Magic
Thanks for the query.
The risk of MS recurence is higher after surgeries and stopping therapy but this is not so high and I dont think that it will happen. He should just focus on recovery from cancer and surgery now.MS should be on second place. He should start with rebif
as soon as he can but as I said it is the most important to stand chemoth now and control malignant disease.
Wish you good health.