Phase I Study of Umbilical Cord Blood Natural Killer (NK) Cell Therapy for Children With High-risk, R/R Neuroblastoma.

This is a phase I prospective clinical trial, including phase Ia and phase Ib. Phase Ia include 3 dose levels, utilizing a 3+3 design principle, and each dose level will enroll at least 3 subjects. The recommended dose for phase Ia was used in phase Ib. Each patient receives two courses of umbilical cord blood NK cell therapy (a total of 8 infusions of umbilical cord blood NK cells) and other therapy.