Relapse after Immunotherapy


Hi, my 12 year old nephew has battled neuroblastoma for just over 4 years now. After several surgeries, endless chemo/trials, it looks very likely we will lose him for good, any day now. I have read a few stories here about relapses right after immunotherapy. My nephew (Thomas) went to Seattle for Car T Cell therapy in Oct 2017. (we live in Montreal Canada). before he left he was actually doing very well and even after he got back, he looked great.
However, a month later, he was in the hospital for almost 2 weeks from pain in his hip and leg. Doctors said there was significant progression in the bone. Thomas has never been in remission at any point. It was a series of slight tumor shrinkage here, progression there. We never had any kind of news to really celebrate. I was just curious as to how many cases there have been of unexpected relapse shortly after immunotherapy. not looking to lay blame. It just struck me as odd to read a couple of stories about it and how it was similar to our case. Please reach out if you have experienced this or have heard of similar cases. I have been speaking to an Oncologist from Houston who is also interested in knowing. He is preparing to run a trial.