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.

Additional Metadata
Persistent URL dx.doi.org/10.1080/0284186x.2019.1581375, hdl.handle.net/1765/117732
Journal Acta Oncologica
Citation
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