Fig. 1

Primary tumor, nodal, and parotid volumes decrease over the course of radiation. This patient is a 54 year-old man with p16-positive cT4N1M0 squamous cell carcinoma of the left tonsil who required adaptive radiotherapy over the course of radiation secondary to significant tumor response and weight loss during treatment noted on review of daily CBCTs. The primary tumor decreased by 25.0% from baseline (A1) to week 5 (A2). The grossly involved nodes decreased by 48.6% from baseline (B1) to week 5 (B2). The left parotid decreased by 37.2% (cyan) and the right parotid (blue) decreased by 41.9% from baseline (C1) to week 5 (C2). Note contraction of the lateral border of the bilateral parotids at time of re-simulation (C2)