목적: Olfactory neuroblastoma (ONB) is a rare cancer originating from the neural crest of the olfactory epithelium. The current standard treatment involves surgical resection with or without radiotherapy. In contrast to other sinonasal tumors, ONB, despite achieving complete response with initial treatment, exhibits a high recurrence rate, particularly with a significant proportion of local and regional failures. In this study, we aim to analyze the failure patterns following initial treatment and investigate potential strategies for enhancing treatment outcomes. 방법:From 1990 to 2023, we retrospectively analyzed patients diagnosed with ONB and treated at Severance Hospital, Seoul, Republic of Korea. Patients without adequate medical records, those for whom primary treatment was incomplete, or those lost to follow-up before evaluating treatment response were excluded. Overall survival (OS) and disease- free survival (DFS) were assessed using the Kaplan–Meier method. Based on treatment response after primary therapy, patients were categorized into Complete Response (CR) and Progressive Disease groups. Among CR patients, further classification was made into No Evidence of Disease (NED), primary lesion recurrence, nodal recurrence, and distant metastasis categories for analysis. Survival curves were compared between groups using the log-rank test. 결과:A total of 44 patients were included in the analysis. When overall survival was stratified by Kadish stage into Low grade (A, B) and High grade (C, D), the 5-year survival rates were 93.0% and 70.9%, respectively, while the 10-year survival rates were 81.7% and 56.7%, respectively, and this difference was statistically significant (p=0.011). Among patients who achieved Complete Remission (CR) and those who experienced recurrence after initial treatment, the Kadish stage was the only statistically significant factor linked to an elevated risk of recurrence (p<0.05). Patient age, histological grade, surgical approach (craniofacial resection, endoscopic surgery, combined surgery), and type of adjuvant treatment were not associated with recurrence. Among patients who initially achieved CR but eventually experienced recurrence, the recurrence pattern was classified as primary lesion recurrence, nodal recurrence, and distant metastasis. Among the 6 patients with nodal recurrence, the time to recurrence was longer (average 38.6 months), and the majority (83%) were initially at Kadish stage C or higher. The sites of recurrence were predominantly ipsilateral neck levels II and III, although occurrences in ipsilateral level I and contralateral level I were also noted. In the analysis focused on Kadish stage C patients (N=20), nodal recurrence was observed in 25% of the total, with a nodal recurrence rate of 29.4% among those who received a CR judgment for initial treatment. When analyzing patients who underwent surgery after initial treatment at stage C, among the 16 patients who received postoperative radiotherapy (including concurrent chemoradiotherapy), 4 included the neck region in the radiotherapy field, and 12 did not. The probability of nodal recurrence in these subgroups was 0% and 41.6%, respectively. 결론:In this retrospective cohort, patients with a high Kadish stage exhibited significantly worse clinical outcomes, particularly emphasizing the necessity to consider nodal recurrence with a long- term duration in these cases. Even in patients without neck nodes at the initial diagnosis, If the stage is C or higher, it may be considered to include elective radiotherapy or neck field in postoperative radiotherapy.