High-dose stereotactic radiotherapy boost in the radical treatment of head and neck tumors

BACKGROUND: The current results of head and neck cancer treatment remain suboptimal therefore, novel approaches are needed to improve its effectiveness. This prospective, single-center study aims to assess the results and safety of combining conventionally fractionated radiotherapy with a high-dose stereotactic radiotherapy boost in radical treatment. METHODS: Twenty-eight patients with head and neck tumors of diverse localizations and histopathologies were recruited. The stereotactic boost was delivered to primary tumors or metastatic nodes up to 6 days before or after conventional radiotherapy. The boost doses ranged from 8 to 18 Gy. RESULTS: A complete response was observed in 25 patients (89%). The response did not depend on boost size or its timing within the regimen. Disease progression caused death in 5 cases. Positive surgical margins increased the risk of metastasis eighteenfold (p = 0.015) and mortality threefold (p = 0.030). A higher Zubrod performance status correlated with greater acute mucosal and skin toxicity. The most severe late complications were carotid blow-out syndrome (with actinomycosis coinfection) and brain necrosis. The risk of late toxicity increased after exceeding a biological effective dose of 143.33 Gy (p = 0.0148). CONCLUSIONS: A boost with a dose of 10 Gy represents a promising treatment option with permissible tolerance, with higher doses offering similar efficacy but greater late toxicity. TRIAL REGISTRATION: The study protocol was approved by the local Bioethics Committee (KB/430 - 87/19) and registered on the ClinicalTrials.gov (NCT06472570) on 25 June 2024.