Neoadjuvant Chemotherapy-Induced Downstaging Enables R0 Craniofacial Combined Resection in AJCC (American Joint Committee on Cancer) Stage IV Olfactory Neuroblastoma: A Case Report of 12-Year Disease-Free Survival.

Olfactory neuroblastoma (ONB), also known as esthesioneuroblastoma, is a rare malignant tumor arising from the olfactory neuroepithelium, and optimal management of advanced cases with extensive intracranial extension remains challenging. Neoadjuvant chemotherapy (NAC) is not routinely recommended in current guidelines but may be considered in selected patients with locally advanced or initially unresectable disease. We report the case of a 36-year-old man who presented with recurrent epistaxis and progressive somnolence. Nasal endoscopy, computed tomography, and magnetic resonance imaging revealed a large mass occupying the nasal cavity and paranasal sinuses with massive extension into the anterior cranial fossa. Endoscopic biopsy confirmed ONB, staged as modified Kadish C, Dulguerov T4N0, according to the American Joint Committee on Cancer (AJCC) 8th edition, as cT4cN0cM0, clinical Stage IV. Following multidisciplinary tumor board review, curative resection as an initial treatment was considered unfeasible due to the marked intracranial extension, NAC with ifosfamide, cisplatin, and etoposide (ICE) was initiated. During NAC, the patient developed grade 3 neutropenia, grade 3 anemia, and grade 4 thrombocytopenia according to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0, requiring granulocyte colony-stimulating factor support and platelet transfusion; however, these toxicities were successfully managed, and five cycles of ICE were completed without delaying surgery. Follow-up imaging demonstrated marked tumor reduction with a substantial decrease of the intracranial component, corresponding to a partial response. Subsequent endoscope-assisted craniofacial resection achieved gross total tumor removal, and histopathological examination of the resected specimen confirmed ONB. Adjuvant three-dimensional conformal radiotherapy with a total dose of 60 Gy in 30 fractions was administered. At 12 years and six months after surgery, the patient remains alive and disease-free. This case suggests that, in carefully selected patients with advanced ONB, NAC can achieve meaningful tumor downstaging and enable curative surgery with durable long-term disease control.