Clinical Study of Eflornithine After Immunotherapy for High-risk Neuroblastoma（CSHEIN）

The investigators plan to recruit 20 participants and divide them into Group A and Group B based on their clinical status. The inclusion criteria for Group A are: newly diagnosed high-risk neuroblastoma (NB) patients who have completed the standard treatment plan (including immunotherapy) and whose disease has reached complete response (CR) or very good partial response (VGPR). The inclusion criteria for Group B are: recurrent or refractory NB patients who have completed any treatment for recurrent disease, or who have achieved disease stability after any salvage or intensification therapy for primary refractory disease, with at least a partial response (PR) as assessed by CT or MRI and negative bone marrow aspiration. There are no restrictions regarding gender or geographic region. Participants must be under 18 years of age. Eligible subjects will be enrolled into the study after receiving the first oral dose of eflornithine, with a total treatment course of 2 years. Follow-up will continue for up to 3 years after completion of eflornithine therapy.