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Description
Breast cancer is the most frequently diagnosed cancer among women, with over 2 million new cases annually [1]. In advanced-stage cases, many patients undergo mastectomy followed by reconstruction with tissue expanders. These devices may remain in the patient’s body for several weeks, during which post-mastectomy radiotherapy is usually initiated. However, due to the presence of metallic components, tissue expanders may introduce heterogeneities in the radiation field, interfering with dose distribution and potentially compromising both target volume coverage and organ-at-risk sparing. In this context, the aim of this study is to analyze the influence of the presence of a tissue expander and its progressive volume increase on dose distribution during 3D conformal breast radiotherapy using Monte Carlo simulation. The modeling of the tissue expander and the breast radiotherapy treatment were performed using Blender software [2]. A female virtual anthropomorphic phantom, as described in ICRP Publication 145 [3], was used. Two scenarios were considered: with and without the presence of the device, to enable comparison of the results. Additionally, the expander volume gradually increased to evaluate the impact of this variable on treatment planning dosimetry. The dose distribution calculations were performed using the TOPAS Monte Carlo code [4]. The analysis of dosimetric parameters related to target volume coverage and absorbed doses to the heart and ipsilateral lung showed variations in dose distribution, with the presence of underdosed regions and hotspots. The results contribute to a better understanding of the effects of breast tissue expanders on dosimetry, supporting clinical decision-making regarding the need for specific planning strategies or treatment adjustments.
[1] Ferlay et al 2024 Global Cancer Observatory: Cancer Today IARC
[2] Blender Foundation 2018 Blender
[3] Kim et al 2020 Ann ICRP 49 13-201
[4] Faddegon et al 2020 Phys Med 72 114–121