Breast radiotherapyMRI-guided single fraction ablative radiotherapy for early-stage breast cancer: a brachytherapy versus volumetric modulated arc therapy dosimetry study
Section snippets
Patient characteristics
This study included patients from the pre-existing NTR3198 study, approved by our institutional review board [7]. Patients with tumors up to 30 mm, scheduled for breast-conserving surgery and whole breast irradiation were included. Baseline characteristics of the 20 patients are shown in Table 1. Patients underwent a contrast-enhanced (CE) CT and CE-MRI in supine RT treatment position on a wedge board at 10° of inclination, with arms in abduction above the head. Details on patient positioning
Results
The tumor and ipsilateral breast characteristics are presented in Table 1. Tumors were mainly laterally located in the left breast. The median tumor size was 13.5 mm, with a median distance of 10.0 mm and 9.0 mm to the skin and chest wall, respectively.
Due to the additional 3 mm PTV margin required with VMAT, IMB resulted in a lower median PTVGTV (1.8 cc vs. 6.1 cc, p < 0.05) and PTVCTV (74.8 cc vs. 100.9 cc, p < 0.05) (Table 2). The median PTVGTV and PTVCTV receiving at least 95% of the prescribed dose
Discussion
A comparative planning study on single fraction treatment was performed to evaluate the dosimetric feasibility of single dose MR-guided ablative radiotherapy for early-stage breast cancer. The VMAT and IMB treatment approach resulted in adequate target volume coverage for all cases. Due to the additional PTV margin required for VMAT, the PTVCTV was significantly lower with IMB. However, the extent of high dose volumes in the PTVCTV was considerably lower with VMAT compared to IMB. Appendix 1B
Conflict of interest
None.
Acknowledgements
This study was supported by a grant from the Pink Ribbon Association. We thank professor E. van Limbergen from the radiation-oncology department at the University Hospital Leuven in Belgium for his remarks on the brachytherapy treatment planning.
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