Clinical Outcomes and Failure Patterns After Postoperative IMRT for Olfactory Neuroblastoma: Late Cervical Nodal Relapse

<h3>Background/Aim:</h3> Olfactory neuroblastoma (ONB) is a rare malignant tumor, and optimal management, particularly the role of elective nodal irradiation (ENI), remains debated. Outcomes and failure patterns after surgery and postoperative radiotherapy were evaluated. <h3>Patients and Methods:</h3> Twenty-one patients with ONB who underwent postoperative radiotherapy at our institution between 2009 and 2022 were retrospectively reviewed. Modified Kadish stage A, B, C, and D disease was identified in three, six, 10, and two patients, respectively. Surgical resection was performed before irradiation in all patients, most often <i>via</i> an endoscopic endonasal approach. Postoperative intensity-modulated radiation therapy (IMRT) with a median dose of 60 Gy was delivered to the primary site in all patients, and three patients also received cervical nodal irradiation. Median follow-up was 81.2 months. <h3>Results:</h3> The 5-year overall survival and disease-free survival rates were 84.7% and 74.6%, respectively. Recurrence developed in six patients, most often in the cervical lymph nodes and bone; no in-field recurrence occurred at the initial failure site. Among 18 clinically N0 patients who did not receive ENI, cervical lymph node recurrence occurred in five (27.8%), increasing to 33.3% in those with modified Kadish stage B or higher disease. Conversely, no nodal recurrence was observed in the three patients who received cervical nodal irradiation. Cervical nodal recurrence was relatively frequent, and three patients experienced repeated recurrences over time despite salvage therapy. <h3>Conclusion:</h3> Postoperative IMRT provided favorable local control in ONB. Nonetheless, late cervical nodal relapse was observed in clinically N0 patients managed without elective nodal therapy, supporting prolonged neck surveillance and multi-institutional studies to define optimal elective nodal management.