The Role of Elective Nodal Irradiation in Treating Clinically Node-Negative Sinonasal Squamous Cell Carcinoma.

Purpose: This study aims to examine the role of elective nodal irradiation (ENI) in clinically node-negative (cN0) sinonasal squamous cell carcinoma (SNSCC) and to define the optimal radiation fields for ENI.
Methods and Materials: We retrospectively reviewed 368 patients with cN0 SNSCC treated between 2009 and 2021. The study evaluated the impact of ENI on overall survival, progression-free survival, regional failure-free survival, and distant metastasis-free survival, along with the coverage areas of ENI.
Results: The majority of patients underwent surgery (316/368, 85.9%), with 276 of 368 (75%) having tumors in the maxillary sinus or nasal cavity and 249 of 368 (67.7%) presenting with T4 disease. Additionally, in 119 of the 368 cases (32.3%), tumors were poorly differentiated. The 5-year overall survival, progression-free survival, regional failure-free survival, and distant metastasis-free survival rates were 59.3%, 54.0%, 57.6%, and 58.8%, respectively. ENI was performed in 217 patients (59%), with 16 experiencing neck relapse during follow-up. Although ENI did not enhance survival rates, it significantly reduced the overall regional failure rate (7.9% vs 1.8%; χ ² = 7.98; P < .01) and the cumulative incidence of regional failure (P = .045). Additionally, the subgroups with maxillary sinus origin (2.3% vs 13.5%; P = .025), T4 stage (1.8% vs 8.5%; P = .028), and poor differentiation (2.4% vs 13.5%; P = .029) had higher cumulative incidences of regional failure in patients without ENI. No significant difference was observed in survival and regional failure rates between patients treated with ENI to levels Ib and II with or without level III, as well as between cN0 patients with nonmidline crossing lesions receiving unilateral or bilateral ENI.
Conclusions: Despite no survival benefit, ENI significantly decreases the regional failure rate in patients with cN0 SNSCC. For primary lesions not crossing the midline, ipsilateral ENI targeting levels Ib and II proves to be an effective strategy.
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