Dosimetric Advantages of Online Adaptive Radiation Therapy for Head and Neck Squamous Cell Carcinoma: Results From a Prospective Registry Study

• Published in: International journal of radiation oncology, biology, physics Vol. 122; no. 4; pp. 917 - 925
• Main Authors: Shi, Julia J., Meduri, Krithi, Liao, Chien-Yi, Moon, Dominic H., Avkshtol, Vladimir, Parsons, David, Zhong, Xinran, Chen, Liyuan, Lin, Mu-Han, Sher, David J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.07.2025
• Subjects: Adult; Aged; Aged, 80 and over; Cone-Beam Computed Tomography - methods; Female; Head and Neck Neoplasms - radiotherapy; Humans; Male; Middle Aged; Organs at Risk - radiation effects; Prospective Studies; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Intensity-Modulated - methods; Registries; Retrospective Studies; Squamous Cell Carcinoma of Head and Neck - diagnostic imaging; Squamous Cell Carcinoma of Head and Neck - radiotherapy
• ISSN: 0360-3016; 1879-355X; 1879-355X
• DOI: 10.1016/j.ijrobp.2025.03.050

Data are limited on the feasibility and dosimetric advantages of cone beam computed tomography-based online adaptive radiation therapy (oART) in head and neck squamous cell carcinoma. In this retrospective analysis, we assessed the dosimetric outcomes in patients receiving definitive radiation therapy and treated with oART at least once during their treatment course. We retrospectively analyzed 69 patients with head and neck squamous cell carcinoma who received definitive-intent treatment and oART using the Varian Ethos system at a single tertiary care institution between September 2021 and March 2024. Dosimetric outcomes were compared using a t test. The coverage and mean doses of the planning target volumes (PTVs) and the dose to organs-at-risk (OARs) was analyzed. Conformality and heterogeneity were compared with the conformality index, maximum hotspot, and the absolute volume receiving 103%, 105%, and 107% of the maximum prescribed dose. Treatment delivery time was also recorded for each fraction. The cohort was primarily comprised of patients diagnosed with oropharynx (n = 46, 66.7%) and larynx/hypopharynx (n = 15, 21.7%) cancers. Adapted plans had significantly improved coverage when using the V100 as the coverage metric (95.83% vs 89.58%, P < .001) for all PTVs and improved D95% (99.63% vs 95.69%, P < .001) and D99% (95.64% vs 87.82%, P < .001) of the PTV70. The adapted plans also had a substantially smaller volume receiving above 103% of the prescription (−19.04 cc, P = .007). There was no significant difference in the dose distributions of any salivary glands, and the differences in other OARs were clinically insignificant. The mean total adaptive workflow time was 17 (SD, 1.9) minutes, and the mean total in-room time was 36 minutes (SD, 2.3 minutes). Online ART is associated with significantly improved coverage and dose homogeneity but not superior OAR sparing. Additional research is needed to optimally select patients for oART and determine the clinical benefits of these dosimetric advantages.