Dosimetric effect of rotational setup errors in volumetric modulated arc therapy and field-in-field treatment of left-sided breast cancer

• Published in: Physica medica 2024-01, Vol.117, p.103203-103203, Article 103203
• Main Authors: Heikkilä, Annele, Boman, Eeva, Rossi, Maija, Vanhanen, Antti, Mankinen, Mikko, Postema, Michiel, Koivumäki, Tuomas
• Format: Article
• Language: English
• Subjects: Breast radiotherapy; DICOM image rotation; Interfraction positioning errors; Medical Physics; Physics; Robustness of VMAT
• ISSN: 1120-1797; 1724-191X
• DOI: 10.1016/j.ejmp.2023.103203

Setup errors are an important factor in the dosimetric accuracy of radiotherapy delivery. In this study, we investigated how rotational setup errors influence the dose distribution in volumetric modulated arc therapy (VMAT) and tangential field-in-field (FiF) treatment of left-sided breast cancer with supraclavicular lymph node involvement in deep inspiration breath hold. Treatment planning computed tomography images and radiotherapy plans of 20 patients were collected retrospectively for the study. Rotational setup errors up to 3° were simulated by rotating the planning images, and the resulting dosimetric changes were calculated. With rotational setup errors up to 3°, the median decrease of V95% to clinical target volume was less than 0.8 percentage point in both VMAT and FiF plans. The dose distribution of the heart and left anterior descending artery was more stable with respect to rotations in VMAT plans compared to FiF plans. Correction of ≥1° setup errors is recommended due to increased doses to the heart and left anterior descending artery after 1° setup errors. •Rotational setup errors were simulated by rotating CT images using a Matlab script.•Clinical target volume dose distribution was robust towards setup errors up to 3°.•Heart and LAD doses were more robust in VMAT plans compared to field-in-field plans.•Intervention tolerance of 1° is recommended for rotational setup errors.