Work

The impact of positioning errors on the dose distribution of hypofractionated radiotherapy for left-sided radical breast cancer

Year: 2026

Type: article

Abstract: Purpose To evaluate the impact of setup errors on the dosimetry of targets and organs at risk (OARs) in the mode of Hypofractionated radiotherapy(HFRT) for left-sided radical breast cancer, particularly on the esophagus, thyroid and left anterior descending artery (LAD). Methods 30 patients were prescribed with 43.5Gy in 15 fractions. Positioning uncertainties were simulated by shifting the isocenter of 3, 5, 7, and 9 mm in six directions. Deviations in dosimetry were analyzed for the supraclavicular and the chest wall clinical target volume (CTV sc and CTV cw ), the heart, the LAD, the esophagus, and the thyroid under different setup errors. Results For D 95% (dose covering 95% of the target volume), the CTV sc and CTV cw were most sensitive to errors in the superior (S) and anterior (A) directions, respectively. As the positioning error increased from 3 to 9 mm, the decrease in D 95% for CTV sc in the S direction increased from 0.40 Gy to 4.49 Gy, while that for CTV cw in the A direction rose from 0.83 Gy to 11.26 Gy. Among OARs, the dose increase in the esophagus and the thyroid were most pronounced in the right (R) direction, while other OARs such as the heart and LAD were most pronounced in the posterior (P) direction. At a 3 mm error in the most sensitive direction, the D mean (mean dose) of the esophagus, thyroid, LAD, heart, and ipsilateral lung increased by 2.24 Gy, 1.28 Gy, 1.57 Gy, 0.26 Gy, and 0.61 Gy, respectively. When the error increased to 9 mm, these increments further rose to 7.20 Gy, 4.59 Gy, 5.60 Gy, 1.29 Gy, and 2.34 Gy. Conclusion The esophagus and thyroid are most sensitive to setup errors in the right direction, while the heart, LAD, and lung are most sensitive to errors in the posterior direction. It is recommended that the setup error tolerance be set at 3 mm for the CTV cw and OARs, whereas for the CTV sc may be relaxed to 5 mm.

Source: Frontiers in Oncology

DOI: 10.3389/fonc.2026.1805689