BACKGROUND: Olfactory neuroblastomas are rare sinonasal tumors that arise from the olfactory epithelium. The authors presented a case of an olfactory neuroblastoma with extensive cranial invasion that demonstrated dramatic response to sorafenib, a tyrosine kinase inhibitor.
METHODS: A 54-year-old man with history of prostate cancer and melanoma presented with left-sided proptosis and was found to have a 6.5-cm Kadish stage D olfactory neuroblastoma with cranial invasion that was refractory to chemotherapy and everolimus. However, it demonstrated dramatic response to sorafenib, causing extensive skull base defects that prompted operative repair. Genomic analysis of the tumor revealed mutations in TSC1 and SUFU. The patient developed disease progression with liver metastases 35 months after starting sorafenib, prompting a change to lenvatinib. He experienced progression of his olfactory neuroblastoma 10 months following this change and died in hospice 1 month later.
CONCLUSIONS: The authors reviewed the clinical presentation and management of a large olfactory neuroblastoma with dramatic response to sorafenib. They highlighted prior uses of targeted therapy in the management of refractory olfactory neuroblastoma within the context of current standard treatment regimens. Targeted therapies may play a vital role in the management of refractory olfactory neuroblastoma.

Olfactory neuroblastoma (ONB) is a rare malignant neoplasm of the sinonasal cavity. Surgery has been and remains a mainstay of treatment for patients with this tumor. Open craniofacial resections have been the treatment of choice for many decades. More recently, experience has been growing with endoscopic approaches in the management of patients with ONB. The object of this study is to report the authors\' experience over the past 11 years with ONB patients treated with purely endonasal endoscopic techniques.
The authors performed a retrospective chart review of 20 consecutive patients with ONB who underwent a completely endonasal endoscopic approach for an oncological tumor resection at their institution between January 2006 and January 2017. Patient demographics, tumor stage, pathological grade, frozen section analysis, permanent margin assessment, perioperative complications, postoperative therapy, length of follow-up, and outcomes at last follow-up were collected and analyzed.
Eighteen patients presented with newly diagnosed disease, with a modified Kadish stage of A in 2 cases, B in 3, C in 11, and D in 2. Two patients presented with recurrent tumors. An average of 25.3 specimens per patient were examined by frozen section analysis. Although analysis of intraoperative frozen section margins was negative in all but 1 case, microscopic foci of tumor were found in 7 cases (35%) on permanent histopathological analysis. Perioperative complications occurred in 7 patients (35%) including 1 patient who developed a cerebrospinal fluid leak; there were no episodes of meningitis. All but 1 patient received postoperative radiotherapy, and 5 patients received postoperative chemotherapy. With a mean follow-up of over 5 years, 19 patients were alive and 1 patient died from an unrelated cause. There were 2 cases of tumor recurrence. The 5-year overall, disease-specific, and recurrence-free survival rates were 92.9%, 100%, and 92.9%, respectively.
The current results provide additional evidence for the continued use of endoscopic procedures in the management of this malignancy.