Olfactory Neuroblastoma in Children and Adolescents: the European Cooperative Study Group for Pediatric Rare Tumors (Expert) Recommendations for Diagnosis and Management (ESCP)

Background and Aims: Olfactory neuroblastoma (ON) is a very rare tumor (incidence of 0.1 per 100, 000 children). It arises from the olfactory neuroepithelium of the nasal cavity, and can be locally aggressive, spreading to the orbital cavity, skull base, and intracranial cavity. Given the rarity of this tumor, no standardized recommendations for the diagnosis and therapeutic management are available in children. In the frame of the European Cooperative Study Group for Pediatric Rare Tumors (EXPERT), we established harmonized recommendations for ON. Methods: A core working group was established within Expert. We reviewed all case series and studies published regarding ON, summarized the evidence, and defined recommendations ranked according to the Consensus Conference Standard Operating Procedure methodology. Due to the rarity of the tumor, recommendations are developed from retrospective studies (level IV), case reports (level V), and personal expertise (level V). Results: Prognosis varies depending on Kadish staging at diagnosis (including dural invasion, regional nodal involvement, distant metastasis); histological Hyams grade, and treatment. A discussion with a group of experts is advised for every new case. A multimodal treatment combining chemotherapy, surgery and radiotherapy (RT) is currently proposed. Indications for chemotherapy concern high-grade lesions, positive or borderline resection margins, cases of tumor relapse, nonoperable tumors and regional or distant metastatic forms. For patients with locally advanced stages, neoadjuvant chemotherapy is advised, followed by local treatments (surgery and RT ± prophylactic nodal RT) and adjuvant chemotherapy. Patients with distant metastasis are treated similarly to the previous group, with the addition of RT on metastatic sites for oligometastatic patients. Conclusions: Tumor extension (Kadish C-D) and the histological grade (Hyams III-IV) represent an unfavorable prognostic and motivate an intensive approach. This ESCP emphases the importance of a multimodal approach for patients with locally advanced stages.