Background/purpose: To determine the efficacy and toxicity profile of a stereotactic body radiotherapy (SBRT) boost as a first line treatment in patients with oropharyngeal squamous cell carcinoma (OPSCC). Materials and methods: We performed a retrospective cohort study in 195 consecutive OPSCC patients with T1-small T3 disease, treated at Erasmus MC between 2009 and 2016 with a SBRT (3 5.5 Gy) boost after 46 Gy IMRT. Primary endpoints were disease-specific survival (DSS) and Grade 3 toxicity (Common Terminology Criteria). The Kaplan-Meier method and Cox regression model were applied to determine rates and risk factors. Results: The median follow-up was 4.3 years. Treatment compliance was high (100%). Rates of 5-year DSS and late grade 3 toxicity were 85% and 28%, respectively. Five-year overall survival was 67%. The most frequently observed toxicities were mucosal ulceration or soft tissue necrosis (n ¼ 30, 5 year 18%), dysphagia or weight loss (n ¼ 18, 5 year 12%) and osteoradionecrosis (n ¼ 11, 5 year 9%). Current smoker status (hazard ratio [HR] ¼ 2.9, p ¼ .001) and Charlson Comorbidity Index 2 (HR ¼ 1.9, p ¼ .03) were was associated with increased toxicity risk. Tooth extraction prior to RT was associated with increased osteoradionecrosis risk (HR ¼ 6.4, p ¼ .006). Conclusion: We reported on outcomes in the largest patient series to date treated with a hypofractionated boost for OPSCC. Efficacy was good with survival rates comparable to conventionally fractionated (chemo)radiotherapy. Grade 3 toxicity profiles showed high rates of soft tissue necrosis and osteoradionecrosis. Strategies to mitigate severe toxicity risks are under investigation to improve the tolerability of the SBRT boost.

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Journal Acta Oncologica
Baker, S, Verduijn, G.M, Petit, S.F, Sewnaik, A, Mast-Kramer, H, Koljenović, S, … Heemsbergen, W.D. (2019). Long-term outcomes following stereotactic body radiotherapy boost for oropharyngeal squamous cell carcinoma. Acta Oncologica, 58(6), 926–933. doi:10.1080/0284186x.2019.1581375