I am so sorry to hear about your story, sadly there are many more treatments available in the US than there are in the rest of the world.
One thing you should do if you can is test for ALK, cause if you have this gene there are some very very promising treatments. In quite a few places it is becoming very common to do broad DNA testing in the case of relapse (looking for more than just ALK) I would recommend that.
The talks @markshirran linked are very good and very current.
There are definitely some kids who make it through relapse, at ANR they were saying 20% of kids are surviving relapse
Wishing you lots of luck