Background: The aim of this study was to evaluate the effectiveness of post-surgical chemotherapy for infants with localized neuroblastoma without MYCN amplification (MNA), and determine whether risk classification using MNA is reasonable. Methods: Four hundred and fourteen eligible patients were registered between 1998 and 2004. Resectable patients in stage 1 and 2A/2B were treated by surgical resection only. Unresectable patients in stage 3 without MNA received either 6 cycles of regimen A or 3 cycles of regimen A plus 3 cycles of regimen C2; regimen A consisted of low doses of cyclophosphamide and vincristine and regimen C consisted of cyclophosphamide, vincristine and pirarubicin before surgical resection. The resectable and unresectable patients were randomly selected to receive post-surgical chemotherapy. The patients with MNA received intensive chemotherapy regimen D2, consisting of cyclophosphamide, vincristine, pirarubicin and cisplatin, and some of them received high-dose chemotherapy with stem cell transplantation. Results: The 5-year event-free survival (5-EFS) rates of stage 1 and 2A/2B patients without MNA were 97.2 and 89.0% respectively (p = 0.02). A total of 31 patients in stage 3 without MNA received post-surgical chemotherapy, and 30 patients did not. The 5-EFS rates of these two groups (96.0 and 96.2%, respectively) were not significantly different (p = 0.869). The 5-EFS rate for localized patients with MNA (n = 6) was 50.0%, and that of patients without MNA was 95.0% (p < 0.001). Conclusion: Post-surgical chemotherapy was therefore unnecessary for localized patients without MNA. This treatment strategy using MNA is considered to be appropriate in infants.
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