Gross tumor volume margin and local control in p16‐positive oropharynx cancer patients treated with intensity modulated proton therapy.

Background: To determine if the extent of high‐dose gross tumor volume (GTV) to clinical target volume (CTV) expansion is associated with local control in patients with p16‐positive oropharynx cancer (p16+ OPC) treated with definitive intensity modulated proton therapy (IMPT). Methods: We performed a retrospective analysis of patients with p16+ OPC treated with IMPT at a single institution between 2016 and 2021. Patients with a pre‐treatment PET–CT and restaging PET–CT within 4 months following completion of IMPT were analyzed. Results: Sixty patients were included for analysis with a median follow‐up of 17 months. The median GTV to CTV expansion was 5 mm (IQR: 2 mm). Thirty‐three percent of patients (20 of 60) did not have a GTV to CTV expansion. There was one local failure within the expansion group (3%). Conclusion: Excellent local control was achieved using IMPT for p16+ OPC independent of GTV expansion. IMPT with minimal target expansions represent a potential harm‐minimization technique for p16‐positive oropharynx cancer. [ABSTRACT FROM AUTHOR]