Postoperative SBRT in the treatment of early-stage oropharyngeal and oral cavity cancers with high-risk margins: A dosimetric comparison of volumetric modulated arc therapy with or without non-coplanar arcs and acute toxicity outcomes from the STEREOPOSTOP GORTEC 2017–03 phase 2 trial

•The STEREOPOSTOP-GORTEC-2017–03 phase 2 trial evaluates postoperative SBRT in case of high risk margins for pT1-T2/N0 oropharyngeal and oral cavity tumors.•On the 10 first patients treated on Novalis, adding non-coplanar arcs resulted in better dosimetric outcomes.•Acute toxicity appears acceptable.•The most common acute toxicity was grade 2 and 3 mucositis.