Fig. 1

a Representative radiotherapy plan for the hypofractionated stereotactic boost of 10 Gy in two fractions. The persistent tumor can be seen with the gross tumor volume in (a) transverse and (b) sagital screenshots delineated by the red line. The lower jawbone, as the organ at risk, is contoured in purple. The final dose distribution takes into account tumor coverage (orange line—77% isodose) while reducing the dose to the lower jawbone