Medical Insurance after remission

I have a miracle son who was in stage IV at the age of nine and now has been in remission for 13 years and will be graduating from college. I have been fortunate enough to keep him on my medical insurance, but now I am scared because he will have to come off mine since he will have completed his higher learning. I told him to make sure he gets employment with a group ins. but he is still too young to understand all the questions he needs to ask in making sure he will receive coverage for prexisting. It is also known that any cancer patient must continue to get their annual check ups even after they have been in remission for sometime since we are not sure of any long term side effects from the agressive treatment of childhood cancer. Any suggestions?