This is a single-arm clinical trial to evaluate the efficacy and safety of quadruple
immunotherapy with natural killer (NK) cells, anti-GD2 antibody, cytokines (interleukin-2
(IL-2) and granulocyte-macrophage colony stimulating factor (GM-CSF)) and retinoid X receptor
gamma (RXRg) agonist spironolactone for paediatric patients with relapsed or refractory
neuroblastoma.