Long-Term Survey of Japanese Children with Recurrent Nephroblastoma: A Report from Japan Children's Cancer Group.

In prospective Japanese studies of pediatric renal tumors, 5-year event-free survival and overall survival (OS) for patients with nephroblastoma ranges from 75-90% and 89-97%, respectively. However, treatments strategies for recurrent nephroblastoma in Japanese patients remain unclear. This retrospective study aimed to inform the development of treatment strategies by analyzing the long-term results and side effects of salvage therapies for recurrent nephroblastoma in Japan. A questionnaire survey involving 41 institutions (74 patients) collected clinical data on recurrent cases reported to the Renal Tumor Committee of the Japan Children's Cancer Group. Survey forms from 54 cases were evaluated. Median time to recurrence was 9.5 months among 51 patients without underlying disorders. Recurrence occurred at lung-only in 18 patients and at other sites in 33. The 5-year OS for all 51 patients was 70.6%, with recurrent disease causing death in 15 patients and one patient dying from treatment-related complications. Patients with lung-only recurrence had higher 5-year OS rates than those with other-site recurrence. Initial chemotherapy intensity also affected prognosis, with lower intensity associated with higher 5-year OS. In 17 survivors with lung-only recurrence, the most frequent treatment approach combined chemotherapy, surgery and radiotherapy. Conventional chemotherapy included platinum-containing regimens and/or Regimen I-based treatment containing cyclophosphamide and etoposide. Salvage therapies showed remarkable effectiveness for patients with lung-only recurrence or low intensity of the initial chemotherapy, highlighting the need to standardize prospective studies for post-recurrence treatment and identify risks of late complications for long-term survivors.