Stereotactic Body Radiation Therapy for Head and Neck Cancers With Perineural Spread

BACKGROUND: Perineural spread (PNS) in head and neck cancer (HNC) is technically challenging due to complex target volumes adjacent to critical organs. Data on stereotactic body radiation therapy (SBRT) for PNS is scarce. METHODS: This retrospective study included patients treated with SBRT for PNS across two centers in the USA and Canada from 2015 to 2025. Endpoints included overall survival (OS), progression-free survival (PFS), local control (LC), and treatment-related toxicity. RESULTS: Thirty-six patients were included, with median follow up of 47.5 months. Two-year OS, PFS, and LC were 79%, 54%, and 72% respectively. Patients with cutaneous squamous cell carcinoma (cSCC) had superior PFS and LC compared with non-cSCC histologies. Adenoid cystic carcinoma (ACC) accounted for the only in-field failures. Grade ≥ 3 toxicity occurred in 22% (8/36), including grade ≥ 3 osteoradionecrosis in 6% (2/36). Temporal lobe necrosis was solely Grade 1-2 (32%). CONCLUSIONS: SBRT demonstrated durable LC for selected patients with PNS, particularly cSCC, while ACC may warrant a dose-escalated approach.