Evaluate the impact of maintenance therapy with eflornithine on event-free survival and overall survival in high-risk neuroblastoma (NB) children after immunotherapy, and assess its safety.

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.

Inclusion Criteria:

1. According to the International Neuroblastoma Risk Group Classification, it has been histologically diagnosed as high-risk NB.
2. Under the age of 18.
3. The disease assessment status is PR (via CT or MRI) and the bone marrow smear is negative.
4. If the residual mass is MIBG negative or MIBG positive and lacks FDG-PET affinity, it is considered evidence that the mass does not represent active disease. Subjects with stable residual tumor mass visible on CT/MRI will be included in the study.
5. Qualified hematological parameters and organ function; Refer to the CI CTC 4.0 adverse reaction grading standard of grade 2 and below.
6. Eflornithine needs to be activated within 120 days after the completion of previous treatment.

Exclusion Criteria:

1. According to the International Neuroblastoma Risk Group Classification, it has been histologically diagnosed as non high risk NB.
2. Prior to enrollment, the disease assessment status was either progressive disease (PD) or relapse (via CT or MRI).
3. Positive bone marrow smear.
4. Hematological parameters and organ function are not qualified, according to the CI CTC 4.0 adverse reaction grading standard of grade 3 or above.
5. The guardian does not agree to participate.

Children with high-risk neuroblastoma