High-dose 131I-MIBG therapy followed by autologous stem cell transplantation in adult-onset metastatic neuroblastoma without an identifiable primary tumor: a case report and systematic review

Neuroblastoma is an embryonal tumor that predominantly affects children, with a median age at diagnosis of 17 months. Adult-onset neuroblastoma is extremely rare and exhibits distinct clinical and biological features, including more aggressive behavior, poorer prognosis, and lack of standardized treatment protocols compared to pediatric cases. Cases without an identifiable primary tumor are exceptionally uncommon. We describe a 35-year-old male who presented with low back pain, anemia, and elevated erythrocyte sedimentation rate (ESR). Diagnostic workup included imaging studies, core needle biopsy with immunohistochemistry, urinary catecholamine metabolite analysis, and 123 I-MIBG scintigraphy. The patient received multimodal therapy consisting of Children’s Oncology Group (COG) protocol chemotherapy, salvage ICE regimen (ifosfamide, carboplatin, etoposide), high-dose 131 I-MIBG therapy, and autologous stem cell transplantation (ASCT). Concurrently, a systematic review following PRISMA 2020 guidelines was performed. PubMed, Scopus, Embase, and Web of Science were searched in September 2026 to identify cases of adult-onset neuroblastoma (≥ 18 years) without a detectable primary tumor. Data on patient demographics, clinical features, treatment, and outcomes were extracted. The patient had widely metastatic, MIBG-avid neuroblastoma involving the bone, bone marrow, pleura, and brain, with rapid disease progression despite initial chemotherapy. He subsequently received high-dose 131 I-MIBG therapy followed by autologous stem cell transplantation (ASCT) but died of pneumonia five months after transplantation. The systematic review identified four previously reported cases, all male, aged 18–63 years. Clinical presentations, metastatic sites, diagnostic approaches, and treatments were heterogeneous. Treatment modalities included surgery, radiotherapy, chemotherapy, 131 I-MIBG therapy, and targeted therapy. Two patients survived, and two died during follow-up. Notably, none of the previously reported patients underwent ASCT. Adult-onset neuroblastoma without an identifiable primary tumor is extremely rare, particularly when a parenchymal brain metastasis is present at diagnosis, and there is no standardized treatment approach. None of the previously reported cases underwent ASCT. Our case adds experience with high-dose 131 I-MIBG followed by ASCT and highlights the need for early functional imaging, catecholamine testing, and further evaluation of treatment strategies in adults.