ESTRO 2025 - Abstract Book

S1043

Clinical – Head & neck

ESTRO 2025

2770

Digital Poster Feasibility of reduced margin daily online adaptive radiotherapy(DART) in head and neck cancer-interim technical analysis of ongoing prospective study Harjot K Bajwa 1 , Rajesh Natte 1 , Naveen M 2 , Suresh Chaudhari 2 , Rahila sherin 2 , Sushil Beriwal 3 1 radiation oncology, American oncology institute, Hyderabad, India. 2 Radiation physics, American oncology institute, Hyderabad, India. 3 radiation oncology, Allegheny health network, Pittsburgh, USA Purpose/Objective: The PTV margin for head and neck cancer for IGRT is usually 3-5 mm. DART may allow us to treat with reduced margin which would further reduce doses to OARs and help reduce morbidities. The goal of this study was to analyze the dosimetric and technical parameters of head and neck cancer patients treated with reduced margins using DART and surface guidance (SGRT) on a single arm prospective study Material/Methods: Head and neck cancer patients requiring definitive or adjuvant radiotherapy and treated using daily online adaptive technique and surface guidance with reduced PTV margins were enrolled on a single arm prospective study. All patient plans included a CTV to PTV margin of 1mm all around and 2mm supero-inferiorly. This report is technical feasibility of first five patients as required under the protocol to ensure reduced margins were feasible without compromising target coverage Results: Five head and neck cancer patients treated using DART trial protocol were included in the analysis. Four patients were treated with definitive chemoradiotherapy (66Gy in 30 fractions to the high risk PTV). One patient received adjuvant radiotherapy (60Gy in 30 fractions to intermediate risk PTV). Daily online adaptive technique was used in all patients with daily surface guidance using open face mask. CBCT was performed in thoracic mode to better visualize the target and neck nodal areas. The adaptive plan was selected over the scheduled plan for all 150 fractions due to improved target coverage or better OAR sparing. The average total adaptive treatment time including time to review and modify the contours was 19 minutes (16 – 22 minutes). The mean V95% to the GTV, high risk PTV (PTV66) and intermediate risk PTV (PTV60) was 100%, 99.5% and 97.5% in the delivered plan. All the organ at risk doses were within the tolerance limits. The mean deviation from the reference surface was 1mm (0 2mm) during treatment delivery and SGRT monitoring. A CBCT was taken after each treatment to monitor the setup variation. The mean of intrafraction movement was 0.34mm in lateral (IQR – 0.4mm), 0.36mm in longitudinal (IQR – 0.4mm) and 0.46mm in vertical (IQR – 0.6mm) direction. All patients completed planned course of treatment Conclusion: Daily online adaptive radiotherapy with reduced PTV margins is feasible and did not compromise target coverage as confirmed by SGRT and post treatment CBCT. The acute and long-term toxicity and outcome data will be evaluated once patient accrual is completed

Keywords: adaptive radiotherapy, head and neck cancer

References:

1. A. Navran, W. Heemsbergen, T. Janssen, et al. The impact of margin reduction on outcome and toxicity in head and neck cancer patients treated with image-guided volumetric modulated arc therapy (VMAT). Radiother Oncol, 130 (2019), pp. 25-31, 10.1016/j.radonc.2018.06.032 2. Blumenfeld, P., Arbit, E., Den, R. et al. Real world clinical experience using daily intelligence-assisted online adaptive radiotherapy for head and neck cancer. Radiat oncol 19, 43 (2024)