What happends in neuroblastoma cancer?

My 5 yr old brother has recently been diagnosed with high risk neuroblastoma cancer he has a tumour on his adrenal gland which had spread to his bone marrow in various parts of his body before the diagnosis , hes had chemotherapy in a 50 day course now and we have already been told that the current chemo has shrunk the tumout a bit and has wiped some of the cancer out of his bone marrow , does this mean that hes going to be oki , and he'll live or is there more complications that can follow? thanks :)