Assessing Radiographic Predictors of Orbital Recurrence in Olfactory Neuroblastoma: A Novel Grading System for Orbital Involvement

Background: Olfactory neuroblastoma (ONB) is a rare malignant neuroendocrine tumor arising from the olfactory epithelium in the sinonasal tract. Achieving negative surgical margins is crucial for improving patient survival, but the propensity of ONB to invade the orbit complicates achieving clear resections. While previously published grading systems exist to guide decisions on orbital-sparing procedures, advances in imaging and surgical techniques necessitate a more nuanced evaluation. This study proposes a new grading system for orbital involvement in ONB to enhance clinical decision-making by assessing differential functional and oncological outcomes.

Methods: Preoperative computed topography (CT) and magnetic resonance (MR) imaging was reviewed by two faculty radiologists specializing in sinonasal malignancy, blinded to patient outcomes and each other’s responses. Medial-to-lateral orbital involvement was graded progressively including: contact with the lamina papyracea, demineralization, bowing of periorbita (considered no periorbita transgression), focal fat involvement between periorbita and extraocular muscle (EOM), contact with EOM, displacement, deformation, visible invasion, extension into intraconal fat, and contact with optic nerve sheath. Anterior-to-posterior involvement was characterized by dividing the orbit into thirds, with boundaries from the posterior edge of the globe to the face of the sphenoid. Lacrimal sac contact and invasion were also assessed.

Results: Thirty-nine patients with ONB and orbital involvement were included in this study. The median age of the cohort was 51 years, and the majority of patients were male (64%). Regarding anterior-posterior characterization, 14 patients (36%) had tumor involvement of the anterior third of the orbit, 14 (36%) had middle third involvement, and 4 (10%) had involvement of the posterior third, with 11 of these patients (28%) having involvement of multiple thirds (i.e. anterior-middle, middle-posterior, or all thirds). Fifteen patients (39%) had bilateral orbital involvement of tumor. Ultimately, 16 patient experienced local recurrence (including 4 patients with orbital recurrence), 18 had regional metastasis, and 7 had distant metastasis, at a median time to recurrence of 40 months. At most recent follow-up, 25 patients were alive, and 14 were dead including 10 patients who died due to disease. In univariate analysis, orbital recurrence was signficantly associated with lacrimal sac contact (HR = 24.47, p = 0.0064), EOM displacement (HR = 19.22, p = 0.011), EOM deformation (HR = 14.92, p = 0.020), contact with the optic nerve sheath (HR = 33.87, p = 0.013), posterior third involvement (HR = 11.16, p = 0.016), and involvement of multiple thirds (HR = 11.27, p = 0.037). On Kaplan–Meier analysis, patients with orbital recurrence had significantly decreased disease-specific (p = 0.00086) and overall survival (p = 0.011) compared to those without orbital recurrence.

Conclusion: Our data suggests that ONB involvement of specific orbital structures, especially those more laterally located within the orbit or within the posterior third of the orbit, may be associated with higher risk for orbital recurrence, which was found to be associated with worse oncologic outcomes. Therefore, this grading criteria may be used to identify patients who need more thorough evaluation for treatment planning, including adjuvant therapy along with close monitoring for recurrence.

Publication History

Article published online:
07 February 2025