First of all, Larry Mullen is probably not going to reply to YOU about YOUR FRIEND's condition because of privacy issues. If your friend has a question about his status, he/she should contact Larry.
Second, every case is individual. The situation obviously depends on any number of things such as the disease itself, how long it has been "gone," the likelihood it will recur, the potential consquences if it does recur, the impact (if any) it currently has on your friend's life, what (if anything) was removed or changed to cure your friend, etc. etc.
You won't get an answer to this question b/c no one can answer it. As noted, if your friend wants an answer, he/she should gather up the relevant medical records and email Larry. I'm pretty sure your friend will get an answer.